diff --git a/app/Console/Commands/BackupExport.php b/app/Console/Commands/BackupExport.php
index 0697982..095b038 100644
--- a/app/Console/Commands/BackupExport.php
+++ b/app/Console/Commands/BackupExport.php
@@ -6,6 +6,8 @@
 use App\Models\CustomerSignature;
 use App\Models\Quote;
 use App\Models\SenderProfile;
+use App\Models\Settlement;
+use App\Models\SettlementSchedule;
 use App\Services\BackupAudit;
 use App\Services\BackupRestorer;
 use Illuminate\Console\Command;
@@ -27,6 +29,8 @@ public function handle(BackupAudit $audit): int
                 'customers' => Customer::all()->toArray(),
                 'customer_signatures' => CustomerSignature::all()->toArray(),
                 'quotes' => Quote::all()->toArray(),
+                'settlements' => Settlement::all()->toArray(),
+                'settlement_schedules' => SettlementSchedule::all()->toArray(),
             ], JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT | JSON_THROW_ON_ERROR);
 
             $output = $this->option('output');
diff --git a/app/Http/Controllers/BackupController.php b/app/Http/Controllers/BackupController.php
index 0087400..c2afd91 100644
--- a/app/Http/Controllers/BackupController.php
+++ b/app/Http/Controllers/BackupController.php
@@ -8,6 +8,8 @@
 use App\Models\CustomerSignature;
 use App\Models\Quote;
 use App\Models\SenderProfile;
+use App\Models\Settlement;
+use App\Models\SettlementSchedule;
 use App\Services\BackupRestorer;
 use App\Services\BackupStorage;
 use Illuminate\Http\JsonResponse;
@@ -84,6 +86,8 @@ public function download(): JsonResponse
             'customers' => Customer::all()->toArray(),
             'customer_signatures' => CustomerSignature::all()->toArray(),
             'quotes' => Quote::all()->toArray(),
+            'settlements' => Settlement::all()->toArray(),
+            'settlement_schedules' => SettlementSchedule::all()->toArray(),
         ]);
     }
 
diff --git a/app/Http/Controllers/SettlementController.php b/app/Http/Controllers/SettlementController.php
new file mode 100644
index 0000000..fe6836b
--- /dev/null
+++ b/app/Http/Controllers/SettlementController.php
@@ -0,0 +1,131 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Models\Settlement;
+use App\Support\SettlementPricing;
+use App\Support\SettlementScheduleGenerator;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Validation\Rule;
+
+class SettlementController extends Controller
+{
+    public function index()
+    {
+        return Settlement::with('settlementSchedules')
+            ->orderByDesc('start_date')
+            ->orderByDesc('id')
+            ->get();
+    }
+
+    public function store(Request $request)
+    {
+        $data = SettlementPricing::apply($this->validated($request));
+
+        $settlement = DB::transaction(function () use ($data) {
+            $settlement = Settlement::create($data);
+            // interval_count 等の DB default を attributes に反映してから各回を生成する。
+            $settlement->refresh();
+            // 新規作成時は過去/未来の区別なく全回を予定データとして持つ。
+            $settlement->settlementSchedules()->createMany(
+                SettlementScheduleGenerator::generate($settlement),
+            );
+
+            return $settlement;
+        });
+
+        return response()->json($settlement->load('settlementSchedules'), 201);
+    }
+
+    public function show(Settlement $settlement)
+    {
+        return $settlement->load('settlementSchedules');
+    }
+
+    public function update(Request $request, Settlement $settlement)
+    {
+        $data = SettlementPricing::apply(array_merge(
+            $settlement->only(['items', 'tax_rate']),
+            $this->validated($request),
+        ));
+
+        DB::transaction(function () use ($settlement, $data) {
+            $settlement->update($data);
+            $settlement->refresh();
+            // 過去回のスナップショットは不変。基準日（今日）以降の回だけ現在条件で作り直す。
+            SettlementScheduleGenerator::sync($settlement);
+        });
+
+        return $settlement->fresh()->load('settlementSchedules');
+    }
+
+    public function destroy(Settlement $settlement)
+    {
+        $settlement->delete();
+
+        return response()->noContent();
+    }
+
+    private function validated(Request $request): array
+    {
+        return $request->validate([
+            // settlement_number は quote_number と同じ扱い（nullable + UNIQUE）。
+            // 未設定（null）は対象外＝番号なし下書きは複数作成可能。
+            'settlement_number' => [
+                'nullable', 'string', 'max:100',
+                Rule::unique('settlements', 'settlement_number')->ignore($request->route('settlement')),
+            ],
+            'subject' => ['nullable', 'string', 'max:255'],
+            // status/interval_count/billing_timing/tax_rate は DB 側が NOT NULL + default。
+            // nullable だと明示的な null が DB エラー(500)になるため、未指定は default に
+            // 任せつつ null は 422 で弾くために sometimes を使う（値が来た時だけ検証する）。
+            'status' => ['sometimes', 'in:draft,active,ended'],
+
+            // 終了条件は必須: end_date か occurrences_count のいずれか（無期限は不可）。
+            'start_date' => ['required', 'date'],
+            'end_date' => ['nullable', 'required_without:occurrences_count', 'date', 'after_or_equal:start_date'],
+            'occurrences_count' => ['nullable', 'required_without:end_date', 'integer', 'min:1'],
+            'interval_unit' => ['required', 'in:month,year'],
+            'interval_count' => ['sometimes', 'integer', 'min:1'],
+            'billing_day' => ['nullable', 'integer', 'between:1,31'],
+            'billing_timing' => ['sometimes', 'in:advance,arrears'],
+
+            'payment_terms' => ['nullable', 'string', 'max:255'],
+            'tax_rate' => ['sometimes', 'integer', 'min:0', 'max:100'],
+            'notes' => ['nullable', 'string'],
+
+            'sender_profile_id' => ['nullable', 'integer'],
+            'sender_company' => ['nullable', 'string', 'max:255'],
+            'sender_zip' => ['nullable', 'string', 'max:20'],
+            'sender_pref' => ['nullable', 'string', 'max:50'],
+            'sender_city' => ['nullable', 'string', 'max:255'],
+            'sender_address1' => ['nullable', 'string', 'max:255'],
+            'sender_address2' => ['nullable', 'string', 'max:255'],
+            'sender_person' => ['nullable', 'string', 'max:255'],
+            'sender_tel' => ['nullable', 'string', 'max:50'],
+            'sender_fax' => ['nullable', 'string', 'max:50'],
+            'sender_logo_url' => ['nullable', 'string'],
+
+            'customer_id' => ['nullable', 'integer'],
+            'customer_name' => ['nullable', 'string', 'max:255'],
+            'customer_department' => ['nullable', 'string', 'max:255'],
+            'customer_person' => ['nullable', 'string', 'max:255'],
+            'customer_zip' => ['nullable', 'string', 'max:20'],
+            'customer_pref' => ['nullable', 'string', 'max:50'],
+            'customer_city' => ['nullable', 'string', 'max:255'],
+            'customer_address1' => ['nullable', 'string', 'max:255'],
+            'customer_address2' => ['nullable', 'string', 'max:255'],
+            'customer_tel' => ['nullable', 'string', 'max:50'],
+
+            'items' => ['nullable', 'array'],
+            'items.*.name' => ['nullable', 'string', 'max:255'],
+            'items.*.spec' => ['nullable', 'string', 'max:255'],
+            'items.*.quantity' => ['nullable', 'numeric'],
+            'items.*.unit' => ['nullable', 'string', 'max:50'],
+            'items.*.standard_price' => ['nullable', 'numeric'],
+            'items.*.unit_price' => ['nullable', 'numeric'],
+            'items.*.total' => ['nullable', 'numeric'],
+        ]);
+    }
+}
diff --git a/app/Http/Controllers/SettlementScheduleController.php b/app/Http/Controllers/SettlementScheduleController.php
new file mode 100644
index 0000000..30ff1a9
--- /dev/null
+++ b/app/Http/Controllers/SettlementScheduleController.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Models\SettlementSchedule;
+use Illuminate\Http\Request;
+
+class SettlementScheduleController extends Controller
+{
+    /**
+     * 各回の請求予定データを取り出す（帳票化はしない。外部が JSON で取得する口）。
+     * フィルタ: ?settlement_id= / ?from= / ?to=（from/to は billing_date に対する範囲）。
+     */
+    public function index(Request $request)
+    {
+        $filters = $request->validate([
+            'settlement_id' => ['nullable', 'integer'],
+            'from' => ['nullable', 'date'],
+            'to' => ['nullable', 'date', 'after_or_equal:from'],
+        ]);
+
+        return SettlementSchedule::query()
+            ->when(isset($filters['settlement_id']), fn ($query) => $query->where('settlement_id', $filters['settlement_id']))
+            ->when($filters['from'] ?? null, fn ($query, $from) => $query->whereDate('billing_date', '>=', $from))
+            ->when($filters['to'] ?? null, fn ($query, $to) => $query->whereDate('billing_date', '<=', $to))
+            ->orderBy('billing_date')
+            ->orderBy('settlement_id')
+            ->orderBy('sequence_no')
+            ->get();
+    }
+}
diff --git a/app/Models/Settlement.php b/app/Models/Settlement.php
new file mode 100644
index 0000000..a4ac36a
--- /dev/null
+++ b/app/Models/Settlement.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+
+class Settlement extends Model
+{
+    protected $guarded = ['id'];
+
+    protected $casts = [
+        'items' => 'array',
+        'start_date' => 'date:Y-m-d',
+        'end_date' => 'date:Y-m-d',
+        'occurrences_count' => 'integer',
+        'interval_count' => 'integer',
+        'billing_day' => 'integer',
+        'tax_rate' => 'integer',
+        'unit_subtotal' => 'integer',
+        'unit_tax_amount' => 'integer',
+        'unit_total_amount' => 'integer',
+    ];
+
+    public function settlementSchedules(): HasMany
+    {
+        return $this->hasMany(SettlementSchedule::class)->orderBy('sequence_no');
+    }
+}
diff --git a/app/Models/SettlementSchedule.php b/app/Models/SettlementSchedule.php
new file mode 100644
index 0000000..8e9b00d
--- /dev/null
+++ b/app/Models/SettlementSchedule.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class SettlementSchedule extends Model
+{
+    protected $guarded = ['id'];
+
+    protected $casts = [
+        'items' => 'array',
+        'sequence_no' => 'integer',
+        'period_start' => 'date:Y-m-d',
+        'period_end' => 'date:Y-m-d',
+        'billing_date' => 'date:Y-m-d',
+        'due_date' => 'date:Y-m-d',
+        'subtotal' => 'integer',
+        'tax_amount' => 'integer',
+        'total_amount' => 'integer',
+    ];
+
+    public function settlement(): BelongsTo
+    {
+        return $this->belongsTo(Settlement::class);
+    }
+}
diff --git a/app/Services/BackupRestorer.php b/app/Services/BackupRestorer.php
index 9032e41..12257d7 100644
--- a/app/Services/BackupRestorer.php
+++ b/app/Services/BackupRestorer.php
@@ -5,15 +5,19 @@
 use Illuminate\Database\QueryException;
 use Illuminate\Support\Arr;
 use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Validator;
 use Illuminate\Validation\ValidationException;
 
 class BackupRestorer
 {
-    /** エクスポート形式のバージョン。2 で customers から customer_signatures を分離した。 */
-    public const VERSION = 2;
+    /**
+     * エクスポート形式のバージョン。
+     * 2 で customers から customer_signatures を分離、3 で settlements / settlement_schedules を追加した。
+     */
+    public const VERSION = 3;
 
     /** 復元を受け付けるバージョン。1 は customers[].customer_signature を含む旧形式。 */
-    public const SUPPORTED_VERSIONS = [1, 2];
+    public const SUPPORTED_VERSIONS = [1, 2, 3];
 
     /**
      * @return array{inserted: int, skipped: int, updated: int, errors: array<int, string>}
@@ -44,13 +48,30 @@ public function restore(array $data, string $mode): array
                 return $row;
             });
 
-            $this->restoreRows('quotes', $data['quotes'] ?? [], $mode, $summary, function (array $row): array {
+            $encodeItems = function (array $row): array {
                 if (isset($row['items']) && is_array($row['items'])) {
                     $row['items'] = json_encode($row['items'], JSON_UNESCAPED_UNICODE);
                 }
 
                 return $row;
-            });
+            };
+
+            $this->restoreRows('quotes', $data['quotes'] ?? [], $mode, $summary, $encodeItems);
+
+            $restoredSettlementIds = $this->restoreRows('settlements', $data['settlements'] ?? [], $mode, $summary, $encodeItems);
+            // JSON decode で int/string どちらにもなり得るため、文字列キーの set で照合する。
+            $restoredSettlementIdSet = array_fill_keys(array_map('strval', $restoredSettlementIds), true);
+
+            $scheduleRows = [];
+            foreach ($data['settlement_schedules'] ?? [] as $row) {
+                if (isset($restoredSettlementIdSet[(string) ($row['settlement_id'] ?? '')])) {
+                    $scheduleRows[] = $row;
+                } else {
+                    // skip された親や存在しない親の予定を、同じIDの別仕切書へ紐付けない。
+                    $summary['skipped']++;
+                }
+            }
+            $this->restoreRows('settlement_schedules', $scheduleRows, $mode, $summary, $encodeItems);
         });
 
         return $summary;
@@ -67,6 +88,15 @@ private function validateRows(array $data): void
             'customers' => ['customer_name'],
             'customer_signatures' => ['customer_id', 'signature'],
             'quotes' => [],
+            'settlements' => ['start_date', 'interval_unit'],
+            'settlement_schedules' => ['settlement_id', 'sequence_no', 'period_start', 'period_end', 'billing_date'],
+        ];
+        $nonNullableDefaultColumns = [
+            'settlements' => [
+                'status', 'interval_count', 'billing_timing', 'tax_rate',
+                'unit_subtotal', 'unit_tax_amount', 'unit_total_amount',
+            ],
+            'settlement_schedules' => ['subtotal', 'tax_amount', 'total_amount'],
         ];
 
         foreach ($requiredColumns as $table => $columns) {
@@ -101,6 +131,56 @@ private function validateRows(array $data): void
                         ]);
                     }
                 }
+
+                // default 付きカラムは省略を許すが、明示的な null / 非スカラ値は DB 例外になるため拒否する。
+                foreach ($nonNullableDefaultColumns[$table] ?? [] as $column) {
+                    if (array_key_exists($column, $row)
+                        && (! is_scalar($row[$column]) || $row[$column] === '')) {
+                        throw ValidationException::withMessages([
+                            'file' => ["{$table}.{$index} の {$column} が不正です。"],
+                        ]);
+                    }
+                }
+
+                if ($table === 'settlements') {
+                    $validator = Validator::make($row, [
+                        'status' => ['sometimes', 'in:draft,active,ended'],
+                        'start_date' => ['required', 'date'],
+                        'end_date' => ['nullable', 'required_without:occurrences_count', 'date', 'after_or_equal:start_date'],
+                        'occurrences_count' => ['nullable', 'required_without:end_date', 'integer', 'min:1'],
+                        'interval_unit' => ['required', 'in:month,year'],
+                        'interval_count' => ['sometimes', 'integer', 'min:1'],
+                        'billing_day' => ['nullable', 'integer', 'between:1,31'],
+                        'billing_timing' => ['sometimes', 'in:advance,arrears'],
+                        'tax_rate' => ['sometimes', 'integer', 'between:0,100'],
+                        'items' => ['nullable', 'array'],
+                    ]);
+                    if ($validator->fails()) {
+                        throw ValidationException::withMessages([
+                            'file' => ["{$table}.{$index} の値が不正です: {$validator->errors()->first()}"],
+                        ]);
+                    }
+                }
+
+                if ($table === 'settlement_schedules') {
+                    $validator = Validator::make($row, [
+                        'settlement_id' => ['required', 'integer', 'min:1'],
+                        'sequence_no' => ['required', 'integer', 'min:1'],
+                        'period_start' => ['required', 'date'],
+                        'period_end' => ['required', 'date', 'after_or_equal:period_start'],
+                        'billing_date' => ['required', 'date'],
+                        'due_date' => ['nullable', 'date'],
+                        'subtotal' => ['sometimes', 'integer'],
+                        'tax_amount' => ['sometimes', 'integer'],
+                        'total_amount' => ['sometimes', 'integer'],
+                        'items' => ['nullable', 'array'],
+                    ]);
+                    if ($validator->fails()) {
+                        throw ValidationException::withMessages([
+                            'file' => ["{$table}.{$index} の値が不正です: {$validator->errors()->first()}"],
+                        ]);
+                    }
+                }
             }
         }
     }
diff --git a/app/Support/SettlementPricing.php b/app/Support/SettlementPricing.php
new file mode 100644
index 0000000..098147f
--- /dev/null
+++ b/app/Support/SettlementPricing.php
@@ -0,0 +1,41 @@
+<?php
+
+namespace App\Support;
+
+use Illuminate\Support\Collection;
+
+class SettlementPricing
+{
+    /**
+     * @param  array  $data  仕切書データ（items, tax_rate を含む）
+     * @return array 1回分の金額と再計算済み items を埋めた配列
+     */
+    public static function apply(array $data): array
+    {
+        $items = collect($data['items'] ?? [])->map(function ($item) {
+            $quantity = (int) ($item['quantity'] ?? 0);
+            $unitPrice = (int) ($item['unit_price'] ?? 0);
+            $item['total'] = $quantity * $unitPrice;
+
+            return $item;
+        });
+
+        $subtotal = $items->sum('total');
+        $taxRate = (int) ($data['tax_rate'] ?? 10);
+        $tax = (int) floor($subtotal * $taxRate / 100);
+
+        $data['items'] = $items->values()->all();
+        $data['unit_subtotal'] = $subtotal;
+        $data['unit_tax_amount'] = $tax;
+        $data['unit_total_amount'] = $subtotal + $tax;
+
+        return $data;
+    }
+
+    public static function subtotal(Collection|array $items): int
+    {
+        return collect($items)->sum(function ($item) {
+            return (int) ($item['quantity'] ?? 0) * (int) ($item['unit_price'] ?? 0);
+        });
+    }
+}
diff --git a/app/Support/SettlementScheduleGenerator.php b/app/Support/SettlementScheduleGenerator.php
new file mode 100644
index 0000000..9fe91e6
--- /dev/null
+++ b/app/Support/SettlementScheduleGenerator.php
@@ -0,0 +1,156 @@
+<?php
+
+namespace App\Support;
+
+use App\Models\Settlement;
+use Carbon\CarbonImmutable;
+use Carbon\CarbonInterface;
+use Illuminate\Database\Eloquent\Collection;
+use Illuminate\Support\Facades\DB;
+use InvalidArgumentException;
+
+class SettlementScheduleGenerator
+{
+    /**
+     * 仕切書の現在の条件から、永続化前の全請求予定を生成する。
+     *
+     * @return array<int, array<string, mixed>>
+     */
+    public static function generate(Settlement $settlement): array
+    {
+        self::assertGeneratable($settlement);
+
+        $startDate = CarbonImmutable::parse($settlement->start_date->toDateString());
+        $endDate = $settlement->end_date
+            ? CarbonImmutable::parse($settlement->end_date->toDateString())
+            : null;
+        $occurrencesCount = $settlement->occurrences_count;
+        $schedules = [];
+
+        for ($index = 0; ; $index++) {
+            $sequenceNo = $index + 1;
+            if ($occurrencesCount !== null && $sequenceNo > $occurrencesCount) {
+                break;
+            }
+
+            // 常に初回開始日から加算し、1月31日などの月末アンカーのドリフトを防ぐ。
+            $periodStart = self::addInterval($startDate, $settlement, $index);
+            if ($endDate && $periodStart->greaterThan($endDate)) {
+                break;
+            }
+
+            $periodEnd = self::addInterval($startDate, $settlement, $index + 1)->subDay();
+            if ($endDate && $periodEnd->greaterThan($endDate)) {
+                $periodEnd = $endDate;
+            }
+
+            $billingDate = self::billingDate($periodStart, $periodEnd, $settlement);
+            $schedules[] = [
+                'sequence_no' => $sequenceNo,
+                'period_start' => $periodStart->toDateString(),
+                'period_end' => $periodEnd->toDateString(),
+                'billing_date' => $billingDate->toDateString(),
+                'due_date' => null,
+                'subtotal' => $settlement->unit_subtotal,
+                'tax_amount' => $settlement->unit_tax_amount,
+                'total_amount' => $settlement->unit_total_amount,
+                'items' => $settlement->items ?? [],
+            ];
+        }
+
+        return $schedules;
+    }
+
+    /**
+     * 基準日より前の回を保持し、当日以降の予定だけを現在条件で置き換える。
+     */
+    public static function sync(Settlement $settlement, ?CarbonInterface $asOf = null): Collection
+    {
+        $cutoff = CarbonImmutable::parse(($asOf ?? now())->toDateString());
+
+        DB::transaction(function () use ($settlement, $cutoff) {
+            $generated = self::generate($settlement);
+            $keptSequenceSet = $settlement->settlementSchedules()
+                ->whereDate('billing_date', '<', $cutoff->toDateString())
+                ->pluck('sequence_no')
+                ->mapWithKeys(fn ($sequenceNo) => [(int) $sequenceNo => true])
+                ->all();
+
+            $settlement->settlementSchedules()
+                ->whereDate('billing_date', '>=', $cutoff->toDateString())
+                ->delete();
+
+            foreach ($generated as $schedule) {
+                if (isset($keptSequenceSet[(int) $schedule['sequence_no']])) {
+                    continue;
+                }
+
+                $settlement->settlementSchedules()->create($schedule);
+            }
+        });
+
+        return $settlement->settlementSchedules()->orderBy('sequence_no')->get();
+    }
+
+    private static function assertGeneratable(Settlement $settlement): void
+    {
+        if (! $settlement->start_date) {
+            throw new InvalidArgumentException('start_date is required.');
+        }
+
+        if (! $settlement->end_date && $settlement->occurrences_count === null) {
+            throw new InvalidArgumentException('end_date or occurrences_count is required.');
+        }
+
+        if ($settlement->end_date && $settlement->end_date->lt($settlement->start_date)) {
+            throw new InvalidArgumentException('end_date must be on or after start_date.');
+        }
+
+        if (! in_array($settlement->interval_unit, ['month', 'year'], true)) {
+            throw new InvalidArgumentException('interval_unit must be month or year.');
+        }
+
+        if ((int) $settlement->interval_count < 1) {
+            throw new InvalidArgumentException('interval_count must be at least 1.');
+        }
+
+        if ($settlement->occurrences_count !== null && $settlement->occurrences_count < 1) {
+            throw new InvalidArgumentException('occurrences_count must be at least 1.');
+        }
+
+        if (! in_array($settlement->billing_timing, ['advance', 'arrears'], true)) {
+            throw new InvalidArgumentException('billing_timing must be advance or arrears.');
+        }
+
+        if ($settlement->billing_day !== null && ($settlement->billing_day < 1 || $settlement->billing_day > 31)) {
+            throw new InvalidArgumentException('billing_day must be between 1 and 31.');
+        }
+    }
+
+    private static function addInterval(
+        CarbonImmutable $startDate,
+        Settlement $settlement,
+        int $multiplier,
+    ): CarbonImmutable {
+        $amount = $settlement->interval_count * $multiplier;
+
+        return $settlement->interval_unit === 'month'
+            ? $startDate->addMonthsNoOverflow($amount)
+            : $startDate->addYearsNoOverflow($amount);
+    }
+
+    private static function billingDate(
+        CarbonImmutable $periodStart,
+        CarbonImmutable $periodEnd,
+        Settlement $settlement,
+    ): CarbonImmutable {
+        $boundary = $settlement->billing_timing === 'arrears' ? $periodEnd : $periodStart;
+        if ($settlement->billing_day === null) {
+            return $boundary;
+        }
+
+        $day = min($settlement->billing_day, $boundary->daysInMonth);
+
+        return $boundary->startOfMonth()->day($day);
+    }
+}
diff --git a/database/migrations/2026_07_08_000001_create_settlements_table.php b/database/migrations/2026_07_08_000001_create_settlements_table.php
new file mode 100644
index 0000000..3af208d
--- /dev/null
+++ b/database/migrations/2026_07_08_000001_create_settlements_table.php
@@ -0,0 +1,65 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('settlements', function (Blueprint $table) {
+            $table->id();
+            $table->string('settlement_number')->nullable()->unique();
+            $table->string('subject')->nullable();
+            $table->string('status')->default('draft');
+            $table->date('start_date');
+            $table->date('end_date')->nullable();
+            $table->unsignedInteger('occurrences_count')->nullable();
+            $table->string('interval_unit');
+            $table->unsignedInteger('interval_count')->default(1);
+            $table->unsignedTinyInteger('billing_day')->nullable();
+            $table->string('billing_timing')->default('advance');
+            $table->string('payment_terms')->nullable();
+            $table->unsignedInteger('tax_rate')->default(10);
+            $table->text('notes')->nullable();
+
+            // 発行者スナップショット
+            $table->foreignId('sender_profile_id')->nullable();
+            $table->string('sender_company')->nullable();
+            $table->string('sender_zip')->nullable();
+            $table->string('sender_pref')->nullable();
+            $table->string('sender_city')->nullable();
+            $table->string('sender_address1')->nullable();
+            $table->string('sender_address2')->nullable();
+            $table->string('sender_person')->nullable();
+            $table->string('sender_tel')->nullable();
+            $table->string('sender_fax')->nullable();
+            $table->longText('sender_logo_url')->nullable();
+
+            // 取引先スナップショット
+            $table->foreignId('customer_id')->nullable();
+            $table->string('customer_name')->nullable();
+            $table->string('customer_department')->nullable();
+            $table->string('customer_person')->nullable();
+            $table->string('customer_zip')->nullable();
+            $table->string('customer_pref')->nullable();
+            $table->string('customer_city')->nullable();
+            $table->string('customer_address1')->nullable();
+            $table->string('customer_address2')->nullable();
+            $table->string('customer_tel')->nullable();
+
+            // 1回分の明細・金額
+            $table->json('items')->nullable();
+            $table->bigInteger('unit_subtotal')->default(0);
+            $table->bigInteger('unit_tax_amount')->default(0);
+            $table->bigInteger('unit_total_amount')->default(0);
+            $table->timestamps();
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('settlements');
+    }
+};
diff --git a/database/migrations/2026_07_08_000002_create_settlement_schedules_table.php b/database/migrations/2026_07_08_000002_create_settlement_schedules_table.php
new file mode 100644
index 0000000..5a64ea5
--- /dev/null
+++ b/database/migrations/2026_07_08_000002_create_settlement_schedules_table.php
@@ -0,0 +1,33 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('settlement_schedules', function (Blueprint $table) {
+            $table->id();
+            $table->foreignId('settlement_id')->constrained()->cascadeOnDelete();
+            $table->unsignedInteger('sequence_no');
+            $table->date('period_start');
+            $table->date('period_end');
+            $table->date('billing_date');
+            $table->date('due_date')->nullable();
+            $table->bigInteger('subtotal')->default(0);
+            $table->bigInteger('tax_amount')->default(0);
+            $table->bigInteger('total_amount')->default(0);
+            $table->json('items')->nullable();
+            $table->timestamps();
+
+            $table->unique(['settlement_id', 'sequence_no']);
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('settlement_schedules');
+    }
+};
diff --git a/resources/js/App.tsx b/resources/js/App.tsx
index b25e6e9..b0fa0e5 100644
--- a/resources/js/App.tsx
+++ b/resources/js/App.tsx
@@ -11,6 +11,9 @@ import QuoteList from './pages/QuoteList';
 import QuoteForm from './pages/QuoteForm';
 import Import from './pages/Import';
 import QuotePreview from './pages/QuotePreview';
+import SettlementList from './pages/SettlementList';
+import SettlementForm from './pages/SettlementForm';
+import SettlementPreview from './pages/SettlementPreview';
 import Summary from './pages/Summary';
 import SenderProfiles from './pages/SenderProfiles';
 import Customers from './pages/Customers';
@@ -74,6 +77,10 @@ export default function App() {
       <Route path="/import" element={<RequireAuth><Import /></RequireAuth>} />
       <Route path="/quotes/:id" element={<RequireAuth><QuotePreview /></RequireAuth>} />
       <Route path="/quotes/:id/edit" element={<RequireAuth><QuoteForm /></RequireAuth>} />
+      <Route path="/settlements" element={<RequireAuth><SettlementList /></RequireAuth>} />
+      <Route path="/settlements/new" element={<RequireAuth><SettlementForm /></RequireAuth>} />
+      <Route path="/settlements/:id" element={<RequireAuth><SettlementPreview /></RequireAuth>} />
+      <Route path="/settlements/:id/edit" element={<RequireAuth><SettlementForm /></RequireAuth>} />
       <Route path="/summary" element={<RequireAuth><Summary /></RequireAuth>} />
       <Route path="/sender-profiles" element={<RequireAuth><SenderProfiles /></RequireAuth>} />
       <Route path="/customers" element={<RequireAuth><Customers /></RequireAuth>} />
diff --git a/resources/js/components/Layout.tsx b/resources/js/components/Layout.tsx
index 981f988..f82a23c 100644
--- a/resources/js/components/Layout.tsx
+++ b/resources/js/components/Layout.tsx
@@ -1,7 +1,7 @@
 import { NavLink, useNavigate } from 'react-router-dom';
 import clsx from 'clsx';
 import {
-  FileText, FilePlus, Upload, BarChart3, Building2, Users, ShieldCheck, LogOut, Leaf, Database, type LucideIcon,
+  FileText, FilePlus, Upload, BarChart3, Building2, Users, ShieldCheck, LogOut, Leaf, Database, Repeat, type LucideIcon,
 } from 'lucide-react';
 import type { ReactNode } from 'react';
 import { useAuth } from '../context/AuthContext';
@@ -24,6 +24,7 @@ const NAV: NavGroup[] = [
       { to: '/', label: '見積書一覧', icon: FileText, end: true },
       { to: '/quotes/new', label: '見積書作成', icon: FilePlus },
       { to: '/import', label: '見積書取込', icon: Upload },
+      { to: '/settlements', label: '仕切書一覧', icon: Repeat },
       { to: '/summary', label: '月末集計', icon: BarChart3 },
     ],
   },
diff --git a/resources/js/components/ui.tsx b/resources/js/components/ui.tsx
index f27b8af..eef68fd 100644
--- a/resources/js/components/ui.tsx
+++ b/resources/js/components/ui.tsx
@@ -87,6 +87,39 @@ export function Select({ className, children, ...props }: SelectHTMLAttributes<H
   );
 }
 
+// ---------- Switch ----------
+interface SwitchProps {
+  checked: boolean;
+  onChange: (checked: boolean) => void;
+  label?: ReactNode;
+  disabled?: boolean;
+}
+export function Switch({ checked, onChange, label, disabled }: SwitchProps) {
+  return (
+    <label className={clsx('inline-flex items-center gap-2 text-sm font-medium text-neutral-700', disabled && 'cursor-not-allowed opacity-40')}>
+      <button
+        type="button"
+        role="switch"
+        aria-checked={checked}
+        disabled={disabled}
+        onClick={() => onChange(!checked)}
+        className={clsx(
+          'relative inline-flex h-6 w-11 shrink-0 items-center rounded-full transition-colors focus:outline-none focus-visible:ring-2 focus-visible:ring-primary focus-visible:ring-offset-2',
+          checked ? 'bg-primary' : 'bg-neutral-200'
+        )}
+      >
+        <span
+          className={clsx(
+            'inline-block h-4 w-4 transform rounded-full bg-white shadow transition-transform',
+            checked ? 'translate-x-6' : 'translate-x-1'
+          )}
+        />
+      </button>
+      {label}
+    </label>
+  );
+}
+
 // ---------- Badge ----------
 export function Badge({ className, children }: { className?: string; children: ReactNode }) {
   return (
diff --git a/resources/js/data/adapters/api.ts b/resources/js/data/adapters/api.ts
index c5f8482..6004c51 100644
--- a/resources/js/data/adapters/api.ts
+++ b/resources/js/data/adapters/api.ts
@@ -5,6 +5,7 @@
 import type {
   AuthUser, BackupPayload, Customer as TCustomer, EntityAdapter, ID, ImportResponse,
   ManagedUser, Quote as TQuote, RestoreCredentialsMode, RestoreResult, SenderProfile as TSenderProfile,
+  Settlement as TSettlement, SettlementSchedule as TSettlementSchedule, SettlementScheduleFilters,
   SetupStatus, StoredBackup, StoredRestoreResult,
 } from '../../types';
 
@@ -88,6 +89,17 @@ function makeEntity<T extends { id: ID }>(path: string): EntityAdapter<T> {
 export const Quote: EntityAdapter<TQuote> = makeEntity<TQuote>('quotes');
 export const Customer: EntityAdapter<TCustomer> = makeEntity<TCustomer>('customers');
 export const SenderProfile: EntityAdapter<TSenderProfile> = makeEntity<TSenderProfile>('sender-profiles');
+export const Settlement: EntityAdapter<TSettlement> = makeEntity<TSettlement>('settlements');
+
+// 各回の請求予定データを取得する（フィルタ: settlement_id / from / to は billing_date に対する範囲）。
+export function listSettlementSchedules(filters: SettlementScheduleFilters = {}): Promise<TSettlementSchedule[]> {
+  const params = new URLSearchParams();
+  if (filters.settlement_id !== undefined && filters.settlement_id !== '') params.set('settlement_id', String(filters.settlement_id));
+  if (filters.from) params.set('from', filters.from);
+  if (filters.to) params.set('to', filters.to);
+  const qs = params.toString();
+  return request<TSettlementSchedule[]>('GET', `/api/settlement-schedules${qs ? `?${qs}` : ''}`);
+}
 
 // 御見積書ファイル（複数可）を multipart/form-data で取り込む。
 // FormData は request() を通さない: JSON 化や手動 Content-Type 付与は
diff --git a/resources/js/data/adapters/local.ts b/resources/js/data/adapters/local.ts
index bee7b3e..23f5621 100644
--- a/resources/js/data/adapters/local.ts
+++ b/resources/js/data/adapters/local.ts
@@ -1,6 +1,10 @@
 // localStorage アダプター（オフライン/デモ/テスト用）。
 // API を使わずブラウザ内で完結する。e2e はこのアダプターで分離性を確保する。
-import type { Customer as TCustomer, EntityAdapter, ID, ImportResponse, ImportResult, LineItem, Quote as TQuote, SenderProfile as TSenderProfile } from '../../types';
+import type {
+  Customer as TCustomer, EntityAdapter, ID, ImportResponse, ImportResult, IntervalUnit, LineItem,
+  Quote as TQuote, SenderProfile as TSenderProfile, Settlement as TSettlement,
+  SettlementSchedule as TSettlementSchedule, SettlementScheduleFilters,
+} from '../../types';
 
 const NS = 'quotes';
 
@@ -89,6 +93,159 @@ SenderProfile.update = async (id, data) => {
   return r;
 };
 
+// --- 仕切書（settlements）と各回の請求予定（settlement_schedules） ---
+// サーバ側 SettlementPricing / SettlementScheduleGenerator と同じ規則
+// （金額再計算、アンカー日からの no-overflow 加算、月末クランプ）を local で再現する。
+// デモ/e2e 用の簡易実装のため、更新時は過去回の保持を行わず全回を作り直す。
+
+const SCHEDULE_KEY = 'settlement_schedules';
+
+function pad2(n: number): string {
+  return String(n).padStart(2, '0');
+}
+
+// 常に初回開始日（アンカー）から加算し、月末周期のドリフトを防ぐ（1/31 + 1ヶ月 → 2/28|29）。
+function addInterval(iso: string, unit: IntervalUnit, amount: number): string {
+  const [y, m, d] = iso.split('-').map(Number);
+  const total = (m - 1) + (unit === 'year' ? amount * 12 : amount);
+  const ny = y + Math.floor(total / 12);
+  const nm = (total % 12) + 1;
+  const daysInMonth = new Date(ny, nm, 0).getDate();
+  return `${ny}-${pad2(nm)}-${pad2(Math.min(d, daysInMonth))}`;
+}
+
+function subDay(iso: string): string {
+  const [y, m, d] = iso.split('-').map(Number);
+  const dt = new Date(y, m - 1, d - 1);
+  return `${dt.getFullYear()}-${pad2(dt.getMonth() + 1)}-${pad2(dt.getDate())}`;
+}
+
+// advance は期首、arrears は期末を基準に、billing_day 指定時は月内日数へクランプする。
+function billingDateOf(periodStart: string, periodEnd: string, s: TSettlement): string {
+  const boundary = s.billing_timing === 'arrears' ? periodEnd : periodStart;
+  if (s.billing_day == null) return boundary;
+  const [y, m] = boundary.split('-').map(Number);
+  const daysInMonth = new Date(y, m, 0).getDate();
+  return `${y}-${pad2(m)}-${pad2(Math.min(s.billing_day, daysInMonth))}`;
+}
+
+// SettlementPricing::apply 相当。items から 1回分の小計・税・税込額を再計算する。
+function applySettlementPricing(data: Partial<TSettlement>): Partial<TSettlement> {
+  const items = (data.items ?? []).map((it) => {
+    const quantity = Math.trunc(Number(it.quantity)) || 0;
+    const unitPrice = Math.trunc(Number(it.unit_price)) || 0;
+    return { ...it, total: quantity * unitPrice };
+  });
+  const subtotal = items.reduce((sum, it) => sum + it.total, 0);
+  const taxRate = Math.trunc(Number(data.tax_rate ?? 10)) || 0;
+  const tax = Math.floor((subtotal * taxRate) / 100);
+  return { ...data, items, unit_subtotal: subtotal, unit_tax_amount: tax, unit_total_amount: subtotal + tax };
+}
+
+// サーバの終了条件バリデーション（end_date/occurrences_count のいずれか必須）を local でも
+// 再現する。ここで弾かないと generateSchedules() が黙って [] を返し、API では 422 になる
+// 入力がローカルでは静かに通ってしまい、デモ/e2e での挙動差がトラブルシュートを難しくする。
+function assertEndCondition(s: Partial<TSettlement>): void {
+  // generateSchedules() は end_date を `!s.end_date` で判定するため、空文字も未設定として扱う。
+  if (s.end_date || s.occurrences_count != null) return;
+  const message = 'end_date か occurrences_count のいずれかが必要です。';
+  const err = new Error(message) as Error & { status?: number; errors?: Record<string, string[]> };
+  err.status = 422;
+  err.errors = { end_date: [message], occurrences_count: [message] };
+  throw err;
+}
+
+// SettlementScheduleGenerator::generate 相当。終了条件が無い場合は生成しない。
+function generateSchedules(s: TSettlement): TSettlementSchedule[] {
+  if (!s.start_date || (!s.end_date && s.occurrences_count == null)) return [];
+  const intervalCount = Number(s.interval_count) || 1;
+  const rows: TSettlementSchedule[] = [];
+
+  for (let index = 0; ; index++) {
+    const sequenceNo = index + 1;
+    if (s.occurrences_count != null && sequenceNo > s.occurrences_count) break;
+
+    const periodStart = addInterval(s.start_date, s.interval_unit, intervalCount * index);
+    if (s.end_date && periodStart > s.end_date) break;
+
+    let periodEnd = subDay(addInterval(s.start_date, s.interval_unit, intervalCount * (index + 1)));
+    if (s.end_date && periodEnd > s.end_date) periodEnd = s.end_date;
+
+    rows.push({
+      id: uid(),
+      settlement_id: s.id,
+      sequence_no: sequenceNo,
+      period_start: periodStart,
+      period_end: periodEnd,
+      billing_date: billingDateOf(periodStart, periodEnd, s),
+      due_date: null,
+      subtotal: s.unit_subtotal ?? 0,
+      tax_amount: s.unit_tax_amount ?? 0,
+      total_amount: s.unit_total_amount ?? 0,
+      items: s.items ?? [],
+    });
+  }
+
+  return rows;
+}
+
+function replaceSchedules(s: TSettlement): void {
+  const others = read<TSettlementSchedule>(SCHEDULE_KEY).filter((r) => String(r.settlement_id) !== String(s.id));
+  write(SCHEDULE_KEY, [...others, ...generateSchedules(s)]);
+}
+
+function schedulesOf(id: ID): TSettlementSchedule[] {
+  return read<TSettlementSchedule>(SCHEDULE_KEY)
+    .filter((r) => String(r.settlement_id) === String(id))
+    .sort((a, b) => a.sequence_no - b.sequence_no);
+}
+
+const settlementBase = makeEntity<TSettlement & Record<string, unknown>>('settlements');
+
+// API と同形状（settlement_schedules を含む）で返す。
+export const Settlement: EntityAdapter<TSettlement> = {
+  async list(sort?: string) {
+    const rows = await settlementBase.list(sort);
+    return rows.map((r) => ({ ...r, settlement_schedules: schedulesOf(r.id) }));
+  },
+  async get(id: ID) {
+    const row = await settlementBase.get(id);
+    return row ? { ...row, settlement_schedules: schedulesOf(row.id) } : null;
+  },
+  async create(data: Partial<TSettlement>) {
+    assertEndCondition(data);
+    const row = await settlementBase.create(applySettlementPricing(data));
+    replaceSchedules(row);
+    return { ...row, settlement_schedules: schedulesOf(row.id) };
+  },
+  async update(id: ID, data: Partial<TSettlement>) {
+    const existing = await settlementBase.get(id);
+    if (!existing) return null;
+    const merged = { ...existing, ...data };
+    assertEndCondition(merged);
+    const row = await settlementBase.update(id, applySettlementPricing(merged));
+    if (!row) return null;
+    replaceSchedules(row);
+    return { ...row, settlement_schedules: schedulesOf(row.id) };
+  },
+  async delete(id: ID) {
+    write(SCHEDULE_KEY, read<TSettlementSchedule>(SCHEDULE_KEY).filter((r) => String(r.settlement_id) !== String(id)));
+    return settlementBase.delete(id);
+  },
+};
+
+// GET /api/settlement-schedules と同じフィルタ・並び順（billing_date 昇順）。
+export async function listSettlementSchedules(filters: SettlementScheduleFilters = {}): Promise<TSettlementSchedule[]> {
+  return read<TSettlementSchedule>(SCHEDULE_KEY)
+    .filter((r) => {
+      if (filters.settlement_id !== undefined && filters.settlement_id !== '' && String(r.settlement_id) !== String(filters.settlement_id)) return false;
+      if (filters.from && r.billing_date < filters.from) return false;
+      if (filters.to && r.billing_date > filters.to) return false;
+      return true;
+    })
+    .sort((a, b) => a.billing_date.localeCompare(b.billing_date) || a.sequence_no - b.sequence_no);
+}
+
 // 取込のモック。ファイル内容の解析はサーバー専用機能のため、local では実ファイルを
 // 解析せず、ファイル名から下書き Quote を 1 件生成して API と同形状の結果を返す。
 // （API モードでの取込結果プレビューと同じ UI を e2e/デモで検証できるようにする）
diff --git a/resources/js/data/store.ts b/resources/js/data/store.ts
index 4fd0301..ddf60c4 100644
--- a/resources/js/data/store.ts
+++ b/resources/js/data/store.ts
@@ -4,12 +4,17 @@
 // 切替: localStorage.setItem('zensales:adapter', 'local')
 import * as apiAdapter from './adapters/api';
 import * as localAdapter from './adapters/local';
-import type { Customer as TCustomer, EntityAdapter, ImportResponse, Quote as TQuote, SenderProfile as TSenderProfile } from '../types';
+import type {
+  Customer as TCustomer, EntityAdapter, ImportResponse, Quote as TQuote, SenderProfile as TSenderProfile,
+  Settlement as TSettlement, SettlementSchedule as TSettlementSchedule, SettlementScheduleFilters,
+} from '../types';
 
 type Adapter = {
   Quote: EntityAdapter<TQuote>;
   Customer: EntityAdapter<TCustomer>;
   SenderProfile: EntityAdapter<TSenderProfile>;
+  Settlement: EntityAdapter<TSettlement>;
+  listSettlementSchedules: (filters?: SettlementScheduleFilters) => Promise<TSettlementSchedule[]>;
   importQuotes: (files: File[]) => Promise<ImportResponse>;
   seedIfEmpty: () => void;
 };
@@ -33,6 +38,8 @@ const adapter = pick();
 export const Quote = adapter.Quote;
 export const Customer = adapter.Customer;
 export const SenderProfile = adapter.SenderProfile;
+export const Settlement = adapter.Settlement;
+export const listSettlementSchedules = adapter.listSettlementSchedules;
 export const importQuotes = adapter.importQuotes;
 export const seedIfEmpty = adapter.seedIfEmpty;
 
diff --git a/resources/js/lib/calc.ts b/resources/js/lib/calc.ts
index e11138b..4395bd5 100644
--- a/resources/js/lib/calc.ts
+++ b/resources/js/lib/calc.ts
@@ -2,7 +2,7 @@
 // subtotal = Σ item.total
 // tax      = floor(subtotal * tax_rate / 100)
 // total    = subtotal + tax
-import type { LineItem, Quote } from '../types';
+import type { LineItem } from '../types';
 
 export function lineTotal(item: Pick<LineItem, 'quantity' | 'unit_price'>): number {
   return Number(item.quantity || 0) * Number(item.unit_price || 0);
@@ -15,7 +15,13 @@ export interface QuoteTotals {
   total: number;
 }
 
-export function quoteTotals(quote: Pick<Quote, 'items' | 'tax_rate'> | null | undefined): QuoteTotals {
+// Quote・Settlement 共通（どちらも items + tax_rate から 1 回分の金額を出す）
+interface Totalable {
+  items?: LineItem[] | null;
+  tax_rate?: number;
+}
+
+export function quoteTotals(quote: Totalable | null | undefined): QuoteTotals {
   const items = quote?.items || [];
   const subtotal = items.reduce((sum, it) => sum + Number(it.total || 0), 0);
   const taxRate = Number(quote?.tax_rate ?? 10);
diff --git a/resources/js/lib/format.ts b/resources/js/lib/format.ts
index 5c6bdec..33149c9 100644
--- a/resources/js/lib/format.ts
+++ b/resources/js/lib/format.ts
@@ -1,5 +1,5 @@
 // 日本語フォーマットユーティリティ
-import type { QuoteStatus } from '../types';
+import type { BillingTiming, IntervalUnit, QuoteStatus, SettlementStatus } from '../types';
 
 export const PREFECTURES: string[] = [
   '北海道', '青森県', '岩手県', '宮城県', '秋田県', '山形県', '福島県',
@@ -34,6 +34,38 @@ export const STATUS_STYLE: Record<QuoteStatus, string> = {
   rejected: 'bg-danger/10 text-danger',
 };
 
+// 仕切書ステータス（issue #58）
+export interface SettlementStatusOption {
+  value: SettlementStatus;
+  label: string;
+}
+
+export const SETTLEMENT_STATUS_OPTIONS: SettlementStatusOption[] = [
+  { value: 'draft', label: '下書き' },
+  { value: 'active', label: '契約中' },
+  { value: 'ended', label: '終了' },
+];
+
+export const SETTLEMENT_STATUS_LABEL: Record<SettlementStatus, string> = Object.fromEntries(
+  SETTLEMENT_STATUS_OPTIONS.map((s) => [s.value, s.label])
+) as Record<SettlementStatus, string>;
+
+export const SETTLEMENT_STATUS_STYLE: Record<SettlementStatus, string> = {
+  draft: 'bg-neutral-100 text-neutral-600',
+  active: 'bg-success/10 text-success',
+  ended: 'bg-neutral-200 text-neutral-500',
+};
+
+export const INTERVAL_UNIT_LABEL: Record<IntervalUnit, string> = {
+  month: 'ヶ月',
+  year: '年',
+};
+
+export const BILLING_TIMING_OPTIONS: { value: BillingTiming; label: string }[] = [
+  { value: 'advance', label: '期首（前払い）' },
+  { value: 'arrears', label: '期末（後払い）' },
+];
+
 export function yen(n: number | string | null | undefined): string {
   const v = Number(n || 0);
   return '¥' + v.toLocaleString('ja-JP');
diff --git a/resources/js/pages/QuoteList.tsx b/resources/js/pages/QuoteList.tsx
index a001b07..a69aedb 100644
--- a/resources/js/pages/QuoteList.tsx
+++ b/resources/js/pages/QuoteList.tsx
@@ -5,7 +5,7 @@ import clsx from 'clsx';
 import { Quote, Customer } from '../data/store';
 import { quoteTotals } from '../lib/calc';
 import { yen, jpDate, STATUS_OPTIONS, STATUS_LABEL, STATUS_STYLE } from '../lib/format';
-import { Button, Card, Input, Select, Badge, EmptyState } from '../components/ui';
+import { Button, Card, Input, Select, Badge, EmptyState, Switch } from '../components/ui';
 import PageHeader from '../components/PageHeader';
 import type { Customer as TCustomer, Quote as TQuote, QuoteStatus } from '../types';
 
@@ -26,6 +26,7 @@ export default function QuoteList() {
   const [query, setQuery] = useState('');
   const [month, setMonth] = useState('');
   const [customerId, setCustomerId] = useState('');
+  const [createAsSettlement, setCreateAsSettlement] = useState(false);
 
   useEffect(() => {
     Quote.list('-created_date').then(setRows);
@@ -55,7 +56,14 @@ export default function QuoteList() {
     <div>
       <PageHeader
         title="見積書一覧"
-        actions={<Button onClick={() => navigate('/quotes/new')}><Plus size={16} />新規作成</Button>}
+        actions={
+          <>
+            <Switch checked={createAsSettlement} onChange={setCreateAsSettlement} label="仕切書として作成" />
+            <Button onClick={() => navigate(createAsSettlement ? '/settlements/new' : '/quotes/new')}>
+              <Plus size={16} />新規作成
+            </Button>
+          </>
+        }
       />
 
       {/* タブ */}
diff --git a/resources/js/pages/SettlementForm.tsx b/resources/js/pages/SettlementForm.tsx
new file mode 100644
index 0000000..6702f55
--- /dev/null
+++ b/resources/js/pages/SettlementForm.tsx
@@ -0,0 +1,323 @@
+import { useEffect, useState, useMemo } from 'react';
+import { useNavigate, useParams, Link } from 'react-router-dom';
+import { Plus, Trash2, ArrowLeft } from 'lucide-react';
+import { Settlement, Customer, SenderProfile } from '../data/store';
+import { quoteTotals, EMPTY_LINE_ITEM } from '../lib/calc';
+import { yen, todayISO, SETTLEMENT_STATUS_OPTIONS, BILLING_TIMING_OPTIONS } from '../lib/format';
+import { Button, Card, Input, Select, Textarea, Field, useToast } from '../components/ui';
+import PageHeader from '../components/PageHeader';
+import type {
+  Customer as TCustomer, LineItem, Settlement as TSettlement, SenderProfile as TSenderProfile,
+} from '../types';
+
+const SENDER_KEYS = ['sender_company', 'sender_zip', 'sender_pref', 'sender_city', 'sender_address1', 'sender_address2', 'sender_person', 'sender_tel', 'sender_fax', 'sender_logo_url'] as const;
+const CUSTOMER_KEYS = ['customer_name', 'customer_department', 'customer_person', 'customer_zip', 'customer_pref', 'customer_city', 'customer_address1', 'customer_address2', 'customer_tel'] as const;
+
+type SettlementForm = Omit<TSettlement, 'id'> & { id?: TSettlement['id'] };
+type EndMode = 'date' | 'count';
+
+function blankSettlement(): SettlementForm {
+  return {
+    settlement_number: '', subject: '', status: 'draft',
+    start_date: todayISO(), end_date: '', occurrences_count: null,
+    interval_unit: 'month', interval_count: 1,
+    billing_day: null, billing_timing: 'advance',
+    payment_terms: '', tax_rate: 10, notes: '',
+    ...(Object.fromEntries(SENDER_KEYS.map((k) => [k, ''])) as Record<(typeof SENDER_KEYS)[number], string>),
+    ...(Object.fromEntries(CUSTOMER_KEYS.map((k) => [k, ''])) as Record<(typeof CUSTOMER_KEYS)[number], string>),
+    sender_profile_id: '', customer_id: '',
+    items: [{ ...EMPTY_LINE_ITEM }],
+  };
+}
+
+export default function SettlementForm() {
+  const { id } = useParams<{ id: string }>();
+  const isEdit = !!id;
+  const navigate = useNavigate();
+  const toast = useToast();
+
+  const [settlement, setSettlement] = useState<SettlementForm>(blankSettlement);
+  const [endMode, setEndMode] = useState<EndMode>('date');
+  const [senders, setSenders] = useState<TSenderProfile[]>([]);
+  const [customers, setCustomers] = useState<TCustomer[]>([]);
+  const [loaded, setLoaded] = useState(!isEdit);
+
+  useEffect(() => {
+    (async () => {
+      const [sp, cs] = await Promise.all([SenderProfile.list(), Customer.list('customer_name')]);
+      setSenders(sp);
+      setCustomers(cs);
+
+      if (isEdit && id) {
+        const s = await Settlement.get(id);
+        if (s) {
+          setSettlement({ ...blankSettlement(), ...s, items: s.items?.length ? s.items : [{ ...EMPTY_LINE_ITEM }] });
+          setEndMode(s.occurrences_count != null ? 'count' : 'date');
+        }
+        setLoaded(true);
+      } else {
+        const def = sp.find((s) => s.is_default) || sp[0];
+        setSettlement((prev) => ({
+          ...prev,
+          ...(def ? applySender(def) : {}),
+          sender_profile_id: def?.id ?? '',
+        }));
+      }
+    })();
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [id]);
+
+  const set = <K extends keyof SettlementForm>(k: K, v: SettlementForm[K]) =>
+    setSettlement((s) => ({ ...s, [k]: v }));
+
+  function applySender(sp: TSenderProfile): Partial<SettlementForm> {
+    return Object.fromEntries(SENDER_KEYS.map((k) => [k, sp[k] ?? ''])) as Partial<SettlementForm>;
+  }
+  function applyCustomer(c: TCustomer): Partial<SettlementForm> {
+    return Object.fromEntries(CUSTOMER_KEYS.map((k) => [k, c[k] ?? ''])) as Partial<SettlementForm>;
+  }
+
+  const onSelectSender = (sid: string) => {
+    const sp = senders.find((s) => String(s.id) === sid);
+    setSettlement((s) => ({
+      ...s,
+      sender_profile_id: sid,
+      ...(sp ? applySender(sp) : Object.fromEntries(SENDER_KEYS.map((k) => [k, '']))),
+    }));
+  };
+  const onSelectCustomer = (cid: string) => {
+    const c = customers.find((x) => String(x.id) === cid);
+    setSettlement((s) => ({
+      ...s,
+      customer_id: cid,
+      ...(c ? applyCustomer(c) : Object.fromEntries(CUSTOMER_KEYS.map((k) => [k, '']))),
+    }));
+  };
+
+  const onSelectEndMode = (mode: EndMode) => {
+    setEndMode(mode);
+    if (mode === 'date') set('occurrences_count', null);
+    else set('end_date', null);
+  };
+
+  // 品目
+  const updateItem = (idx: number, key: keyof LineItem, value: string) => {
+    setSettlement((s) => {
+      const items = (s.items ?? []).map((it, i) => {
+        if (i !== idx) return it;
+        const next = { ...it, [key]: value } as LineItem;
+        if (key === 'quantity' || key === 'unit_price') {
+          next.total = Number(next.quantity || 0) * Number(next.unit_price || 0);
+        }
+        return next;
+      });
+      return { ...s, items };
+    });
+  };
+  const addItem = () => setSettlement((s) => ({ ...s, items: [...(s.items ?? []), { ...EMPTY_LINE_ITEM }] }));
+  const removeItem = (idx: number) => setSettlement((s) => ({ ...s, items: (s.items ?? []).filter((_, i) => i !== idx) }));
+
+  const totals = useMemo(() => quoteTotals(settlement), [settlement]);
+
+  const save = async () => {
+    if (!settlement.customer_name) { toast('取引先を選択してください', 'error'); return; }
+    if (!settlement.start_date) { toast('開始日を入力してください', 'error'); return; }
+    if (endMode === 'date' && !settlement.end_date) { toast('終了日を入力してください', 'error'); return; }
+    if (endMode === 'count' && !settlement.occurrences_count) { toast('回数を入力してください', 'error'); return; }
+
+    // API は settlement_number を nullable+UNIQUE、sender_profile_id/customer_id を
+    // nullable+integer で検証するため、未選択/未入力の "" は null に正規化して送る
+    // （"" のままだと UNIQUE 制約や integer バリデーションに引っかかる）。
+    const payload = {
+      ...settlement,
+      settlement_number: settlement.settlement_number || null,
+      sender_profile_id: settlement.sender_profile_id || null,
+      customer_id: settlement.customer_id || null,
+    };
+    if (isEdit && id) {
+      await Settlement.update(id, payload);
+      toast('仕切書を更新しました');
+      navigate(`/settlements/${id}`);
+    } else {
+      const created = await Settlement.create(payload);
+      toast('仕切書を作成しました');
+      navigate(`/settlements/${created.id}`);
+    }
+  };
+
+  if (!loaded) return <div className="py-20 text-center text-sm text-neutral-400">読み込み中...</div>;
+
+  const num = (v: number | string | null | undefined): number | string => (v === 0 || v ? v : '');
+
+  return (
+    <div>
+      <PageHeader
+        title={isEdit ? '仕切書編集' : '仕切書作成'}
+        actions={
+          <>
+            <Button variant="secondary" onClick={() => navigate(-1)}><ArrowLeft size={16} />戻る</Button>
+            <Button onClick={save}>保存</Button>
+          </>
+        }
+      />
+
+      <div className="grid gap-5 lg:grid-cols-3">
+        <div className="space-y-5 lg:col-span-2">
+          {/* 発行者 / 取引先 */}
+          <Card className="p-5">
+            <div className="grid gap-4 sm:grid-cols-2">
+              <div>
+                <Field label="発行者">
+                  <Select value={String(settlement.sender_profile_id ?? '')} onChange={(e) => onSelectSender(e.target.value)}>
+                    <option value="">発行者を選択</option>
+                    {senders.map((s) => <option key={s.id} value={s.id}>{s.sender_company}</option>)}
+                  </Select>
+                </Field>
+                {senders.length === 0 && (
+                  <p className="mt-1 text-xs text-warning">
+                    ※ 発行者が未登録です。<Link to="/sender-profiles" className="underline">基本情報マスタ</Link> から登録してください。
+                  </p>
+                )}
+              </div>
+              <div>
+                <Field label="取引先" required>
+                  <Select value={String(settlement.customer_id ?? '')} onChange={(e) => onSelectCustomer(e.target.value)}>
+                    <option value="">取引先を選択</option>
+                    {customers.map((c) => <option key={c.id} value={c.id}>{c.customer_name}</option>)}
+                  </Select>
+                </Field>
+                {customers.length === 0 && (
+                  <p className="mt-1 text-xs text-warning">
+                    ※ 取引先が未登録です。<Link to="/customers" className="underline">取引先マスタ</Link> から登録してください。
+                  </p>
+                )}
+              </div>
+            </div>
+          </Card>
+
+          {/* 仕切書情報 */}
+          <Card className="p-5">
+            <h2 className="mb-4 text-sm font-bold text-neutral-700">仕切書情報</h2>
+            <div className="grid gap-4 sm:grid-cols-2">
+              <Field label="仕切書番号" hint="未入力可（番号なし下書き）">
+                <Input value={settlement.settlement_number ?? ''} onChange={(e) => set('settlement_number', e.target.value)} />
+              </Field>
+              <Field label="ステータス">
+                <Select value={settlement.status} onChange={(e) => set('status', e.target.value as TSettlement['status'])}>
+                  {SETTLEMENT_STATUS_OPTIONS.map((s) => <option key={s.value} value={s.value}>{s.label}</option>)}
+                </Select>
+              </Field>
+              <div className="sm:col-span-2">
+                <Field label="件名"><Input value={settlement.subject ?? ''} onChange={(e) => set('subject', e.target.value)} placeholder="件名を入力" /></Field>
+              </div>
+
+              <Field label="開始日" required>
+                <Input type="date" value={settlement.start_date} onChange={(e) => set('start_date', e.target.value)} />
+              </Field>
+              <Field label="終了条件" required>
+                <div className="flex items-center gap-3">
+                  <Select aria-label="終了条件の種類" className="w-32 shrink-0" value={endMode} onChange={(e) => onSelectEndMode(e.target.value as EndMode)}>
+                    <option value="date">終了日</option>
+                    <option value="count">回数</option>
+                  </Select>
+                  {endMode === 'date' ? (
+                    <Input type="date" value={settlement.end_date ?? ''} onChange={(e) => set('end_date', e.target.value)} />
+                  ) : (
+                    <Input type="number" min={1} value={num(settlement.occurrences_count)} onChange={(e) => set('occurrences_count', e.target.value ? Number(e.target.value) : null)} placeholder="回数" />
+                  )}
+                </div>
+              </Field>
+
+              <Field label="頻度" required>
+                <div className="flex items-center gap-2">
+                  <Input type="number" min={1} className="w-20" value={num(settlement.interval_count)} onChange={(e) => set('interval_count', Number(e.target.value) || 1)} />
+                  <Select value={settlement.interval_unit} onChange={(e) => set('interval_unit', e.target.value as TSettlement['interval_unit'])}>
+                    <option value="month">ヶ月ごと</option>
+                    <option value="year">年ごと</option>
+                  </Select>
+                </div>
+              </Field>
+              <Field label="請求タイミング">
+                <Select value={settlement.billing_timing} onChange={(e) => set('billing_timing', e.target.value as TSettlement['billing_timing'])}>
+                  {BILLING_TIMING_OPTIONS.map((o) => <option key={o.value} value={o.value}>{o.label}</option>)}
+                </Select>
+              </Field>
+
+              <Field label="請求日" hint="毎月何日に請求するか（未入力は期首/期末の日付をそのまま使用）">
+                <Input type="number" min={1} max={31} value={num(settlement.billing_day)} onChange={(e) => set('billing_day', e.target.value ? Number(e.target.value) : null)} placeholder="例: 31" />
+              </Field>
+              <Field label="御支払条件"><Input value={settlement.payment_terms ?? ''} onChange={(e) => set('payment_terms', e.target.value)} placeholder="例: 月末締め翌月末払い" /></Field>
+            </div>
+          </Card>
+
+          {/* 品目（1回あたり） */}
+          <Card className="p-5">
+            <div className="mb-3 flex items-center justify-between">
+              <h2 className="text-sm font-bold text-neutral-700">品目（1回あたり）</h2>
+              <Button size="sm" variant="secondary" onClick={addItem}><Plus size={14} />品目を追加</Button>
+            </div>
+            <div className="overflow-x-auto">
+              <div className="min-w-[640px]">
+                <div className="grid grid-cols-12 gap-2 border-b border-neutral-100 pb-2 text-xs font-medium text-neutral-500">
+                  <div className="col-span-3">品名</div>
+                  <div className="col-span-2">仕様</div>
+                  <div className="col-span-1">数量</div>
+                  <div className="col-span-1">単位</div>
+                  <div className="col-span-2">標準価格</div>
+                  <div className="col-span-2">納入単価</div>
+                  <div className="col-span-1 text-right">金額</div>
+                </div>
+                {(settlement.items ?? []).map((it, idx) => (
+                  <div key={idx} className="grid grid-cols-12 items-center gap-2 border-b border-neutral-50 py-2">
+                    <div className="col-span-3"><Input value={it.name} onChange={(e) => updateItem(idx, 'name', e.target.value)} /></div>
+                    <div className="col-span-2"><Input value={it.spec} onChange={(e) => updateItem(idx, 'spec', e.target.value)} /></div>
+                    <div className="col-span-1"><Input type="number" value={num(it.quantity)} onChange={(e) => updateItem(idx, 'quantity', e.target.value)} /></div>
+                    <div className="col-span-1"><Input value={it.unit} onChange={(e) => updateItem(idx, 'unit', e.target.value)} placeholder="個" /></div>
+                    <div className="col-span-2"><Input type="number" value={num(it.standard_price)} onChange={(e) => updateItem(idx, 'standard_price', e.target.value)} /></div>
+                    <div className="col-span-2"><Input type="number" value={num(it.unit_price)} onChange={(e) => updateItem(idx, 'unit_price', e.target.value)} /></div>
+                    <div className="col-span-1 flex items-center justify-end gap-1 text-right text-xs">
+                      <span className="text-neutral-700">{yen(it.total)}</span>
+                      {(settlement.items ?? []).length > 1 && (
+                        <button onClick={() => removeItem(idx)} className="text-neutral-300 hover:text-danger"><Trash2 size={14} /></button>
+                      )}
+                    </div>
+                  </div>
+                ))}
+              </div>
+            </div>
+          </Card>
+
+          {/* 備考 */}
+          <Card className="p-5">
+            <Field label="備考">
+              <Textarea value={settlement.notes ?? ''} onChange={(e) => set('notes', e.target.value)} placeholder="備考・特記事項" />
+            </Field>
+          </Card>
+        </div>
+
+        {/* 金額サマリー */}
+        <div>
+          <Card className="sticky top-8 p-5">
+            <h2 className="mb-4 text-sm font-bold text-neutral-700">1回あたり金額</h2>
+            <dl className="space-y-2 text-sm">
+              <div className="flex justify-between"><dt className="text-neutral-500">小計</dt><dd className="font-medium">{yen(totals.subtotal)}</dd></div>
+              <div className="flex items-center justify-between">
+                <dt className="flex items-center gap-2 text-neutral-500">
+                  消費税
+                  <span className="inline-flex items-center gap-1">
+                    <Input type="number" value={num(settlement.tax_rate)} onChange={(e) => set('tax_rate', Number(e.target.value))} className="w-16 px-2 py-1 text-right" />%
+                  </span>
+                </dt>
+                <dd className="font-medium">{yen(totals.tax)}</dd>
+              </div>
+              <div className="mt-3 flex justify-between border-t border-neutral-100 pt-3 text-base">
+                <dt className="font-bold text-neutral-700">合計</dt>
+                <dd className="font-bold text-primary-700">{yen(totals.total)}</dd>
+              </div>
+            </dl>
+          </Card>
+        </div>
+      </div>
+    </div>
+  );
+}
diff --git a/resources/js/pages/SettlementList.tsx b/resources/js/pages/SettlementList.tsx
new file mode 100644
index 0000000..d8b5f40
--- /dev/null
+++ b/resources/js/pages/SettlementList.tsx
@@ -0,0 +1,138 @@
+import { useEffect, useState } from 'react';
+import { useNavigate } from 'react-router-dom';
+import { Plus, Search, Repeat } from 'lucide-react';
+import clsx from 'clsx';
+import { Settlement, Customer } from '../data/store';
+import { quoteTotals } from '../lib/calc';
+import {
+  yen, jpDate, SETTLEMENT_STATUS_OPTIONS, SETTLEMENT_STATUS_LABEL, SETTLEMENT_STATUS_STYLE, INTERVAL_UNIT_LABEL,
+} from '../lib/format';
+import { Button, Card, Input, Select, Badge, EmptyState } from '../components/ui';
+import PageHeader from '../components/PageHeader';
+import type { Customer as TCustomer, Settlement as TSettlement, SettlementStatus } from '../types';
+
+type TabValue = 'all' | SettlementStatus;
+const TABS: { value: TabValue; label: string }[] = [{ value: 'all', label: 'すべて' }, ...SETTLEMENT_STATUS_OPTIONS];
+
+function periodLabel(row: TSettlement): string {
+  const end = row.end_date ? jpDate(row.end_date) : (row.occurrences_count ? `全${row.occurrences_count}回` : '');
+  return end ? `${jpDate(row.start_date)} 〜 ${end}` : jpDate(row.start_date);
+}
+
+export default function SettlementList() {
+  const navigate = useNavigate();
+  const [rows, setRows] = useState<TSettlement[]>([]);
+  const [customers, setCustomers] = useState<TCustomer[]>([]);
+  const [tab, setTab] = useState<TabValue>('all');
+  const [query, setQuery] = useState('');
+  const [customerId, setCustomerId] = useState('');
+
+  useEffect(() => {
+    Settlement.list('-start_date').then(setRows);
+    Customer.list('customer_name').then(setCustomers);
+  }, []);
+
+  const counts = TABS.reduce<Record<TabValue, number>>((acc, t) => {
+    acc[t.value] = t.value === 'all' ? rows.length : rows.filter((r) => r.status === t.value).length;
+    return acc;
+  }, {} as Record<TabValue, number>);
+
+  const selectedCustomer = customers.find((c) => String(c.id) === customerId);
+  const matchesCustomer = (r: TSettlement) =>
+    !selectedCustomer || String(r.customer_id) === customerId || r.customer_name === selectedCustomer.customer_name;
+
+  const filtered = rows
+    .filter((r) => tab === 'all' || r.status === tab)
+    .filter((r) => !query || r.customer_name?.includes(query) || r.settlement_number?.includes(query) || r.subject?.includes(query))
+    .filter(matchesCustomer);
+
+  return (
+    <div>
+      <PageHeader
+        title="仕切書一覧"
+        actions={<Button onClick={() => navigate('/settlements/new')}><Plus size={16} />新規作成</Button>}
+      />
+
+      {/* タブ */}
+      <div className="mb-4 flex flex-wrap gap-1 border-b border-neutral-200">
+        {TABS.map((t) => (
+          <button
+            key={t.value}
+            onClick={() => setTab(t.value)}
+            className={clsx(
+              '-mb-px border-b-2 px-4 py-2 text-sm font-medium transition-colors',
+              tab === t.value
+                ? 'border-primary text-primary-700'
+                : 'border-transparent text-neutral-500 hover:text-neutral-700'
+            )}
+          >
+            {t.label} <span className="text-neutral-400">{counts[t.value]}</span>
+          </button>
+        ))}
+      </div>
+
+      <div className="mb-4 flex flex-wrap items-center gap-3">
+        <div className="relative max-w-sm flex-1 basis-56">
+          <Search size={16} className="absolute left-3 top-1/2 -translate-y-1/2 text-neutral-400" />
+          <Input className="pl-9" placeholder="取引先・仕切書番号で検索..." value={query} onChange={(e) => setQuery(e.target.value)} />
+        </div>
+        <Select className="w-auto" aria-label="取引先で絞り込み" value={customerId} onChange={(e) => setCustomerId(e.target.value)}>
+          <option value="">すべての取引先</option>
+          {customers.map((c) => <option key={c.id} value={String(c.id)}>{c.customer_name}</option>)}
+        </Select>
+        <span className="ml-auto text-sm text-neutral-500">{filtered.length}件の仕切書</span>
+      </div>
+
+      {filtered.length === 0 ? (
+        <Card>
+          {rows.length === 0 ? (
+            <EmptyState icon={Repeat} title="仕切書がありません">
+              <Button onClick={() => navigate('/settlements/new')}><Plus size={16} />新規作成</Button>
+            </EmptyState>
+          ) : (
+            <EmptyState icon={Search} title="条件に一致する仕切書がありません" />
+          )}
+        </Card>
+      ) : (
+        <Card className="overflow-hidden">
+          <table className="w-full text-sm">
+            <thead>
+              <tr className="border-b border-neutral-100 text-left text-xs text-neutral-500">
+                <th className="px-5 py-3 font-medium">仕切書番号</th>
+                <th className="px-5 py-3 font-medium">取引先 / 件名</th>
+                <th className="px-5 py-3 font-medium">期間</th>
+                <th className="px-5 py-3 font-medium">頻度</th>
+                <th className="px-5 py-3 font-medium text-right">1回あたり金額</th>
+                <th className="px-5 py-3 font-medium">ステータス</th>
+              </tr>
+            </thead>
+            <tbody>
+              {filtered.map((row) => {
+                const { total } = quoteTotals(row);
+                return (
+                  <tr
+                    key={row.id}
+                    onClick={() => navigate(`/settlements/${row.id}`)}
+                    className="cursor-pointer border-b border-neutral-50 last:border-0 hover:bg-neutral-50"
+                  >
+                    <td className="px-5 py-3 font-mono text-xs text-neutral-600">{row.settlement_number || '—'}</td>
+                    <td className="px-5 py-3">
+                      <div className="font-medium text-neutral-800">{row.customer_name || '—'}</div>
+                      <div className="text-xs text-neutral-400">{row.subject || ''}</div>
+                    </td>
+                    <td className="px-5 py-3 text-neutral-500">{periodLabel(row)}</td>
+                    <td className="px-5 py-3 text-neutral-500">{row.interval_count}{INTERVAL_UNIT_LABEL[row.interval_unit]}ごと</td>
+                    <td className="px-5 py-3 text-right font-medium text-neutral-800">{yen(total)}</td>
+                    <td className="px-5 py-3">
+                      <Badge className={SETTLEMENT_STATUS_STYLE[row.status]}>{SETTLEMENT_STATUS_LABEL[row.status]}</Badge>
+                    </td>
+                  </tr>
+                );
+              })}
+            </tbody>
+          </table>
+        </Card>
+      )}
+    </div>
+  );
+}
diff --git a/resources/js/pages/SettlementPreview.tsx b/resources/js/pages/SettlementPreview.tsx
new file mode 100644
index 0000000..a9490b5
--- /dev/null
+++ b/resources/js/pages/SettlementPreview.tsx
@@ -0,0 +1,197 @@
+import { useEffect, useState } from 'react';
+import { useParams, useNavigate } from 'react-router-dom';
+import { Pencil, Trash2, ArrowLeft } from 'lucide-react';
+import { Settlement } from '../data/store';
+import { quoteTotals } from '../lib/calc';
+import { yen, number, jpDate, fullAddress, SETTLEMENT_STATUS_LABEL, SETTLEMENT_STATUS_STYLE, INTERVAL_UNIT_LABEL, BILLING_TIMING_OPTIONS } from '../lib/format';
+import { Button, Card, Badge, Modal, EmptyState, useToast } from '../components/ui';
+import PageHeader from '../components/PageHeader';
+import type { Settlement as TSettlement } from '../types';
+
+export default function SettlementPreview() {
+  const { id } = useParams<{ id: string }>();
+  const navigate = useNavigate();
+  const toast = useToast();
+  const [settlement, setSettlement] = useState<TSettlement | null | undefined>(undefined);
+  const [confirmDelete, setConfirmDelete] = useState(false);
+
+  useEffect(() => {
+    if (id) Settlement.get(id).then((s) => setSettlement(s ?? null));
+  }, [id]);
+
+  if (settlement === undefined) return <div className="py-20 text-center text-sm text-neutral-400">読み込み中...</div>;
+  if (settlement === null) {
+    return (
+      <Card>
+        <EmptyState title="仕切書が見つかりません">
+          <Button onClick={() => navigate('/settlements')}><ArrowLeft size={16} />一覧に戻る</Button>
+        </EmptyState>
+      </Card>
+    );
+  }
+
+  const { subtotal, taxRate, tax, total } = quoteTotals(settlement);
+  const items = settlement.items || [];
+  const schedules = [...(settlement.settlement_schedules ?? [])].sort((a, b) => a.sequence_no - b.sequence_no);
+  const billingTimingLabel = BILLING_TIMING_OPTIONS.find((o) => o.value === settlement.billing_timing)?.label ?? '';
+  const endLabel = settlement.end_date ? jpDate(settlement.end_date) : (settlement.occurrences_count ? `全${settlement.occurrences_count}回` : '—');
+
+  const remove = async () => {
+    if (!id) return;
+    await Settlement.delete(id);
+    toast('仕切書を削除しました');
+    navigate('/settlements');
+  };
+
+  return (
+    <div>
+      <div className="mb-5 flex flex-wrap items-center justify-between gap-2">
+        <Button variant="secondary" onClick={() => navigate('/settlements')}><ArrowLeft size={16} />一覧に戻る</Button>
+        <div className="flex gap-2">
+          <Button variant="secondary" onClick={() => navigate(`/settlements/${id}/edit`)}><Pencil size={16} />編集</Button>
+          <Button variant="outlineDanger" onClick={() => setConfirmDelete(true)}><Trash2 size={16} />削除</Button>
+        </div>
+      </div>
+
+      <PageHeader
+        title={settlement.subject || '仕切書詳細'}
+        actions={<Badge className={SETTLEMENT_STATUS_STYLE[settlement.status]}>{SETTLEMENT_STATUS_LABEL[settlement.status]}</Badge>}
+      />
+
+      <div className="grid gap-5 lg:grid-cols-3">
+        <div className="space-y-5 lg:col-span-2">
+          {/* 基本情報 */}
+          <Card className="p-5">
+            <h2 className="mb-4 text-sm font-bold text-neutral-700">基本情報</h2>
+            <table className="w-full text-sm">
+              <tbody>
+                <MetaRow label="仕切書番号" value={settlement.settlement_number || '—'} />
+                <MetaRow label="取引先" value={settlement.customer_name} />
+                <MetaRow label="発行者" value={settlement.sender_company} />
+                <MetaRow label="開始日" value={jpDate(settlement.start_date)} />
+                <MetaRow label="終了条件" value={endLabel} />
+                <MetaRow label="頻度" value={`${settlement.interval_count}${INTERVAL_UNIT_LABEL[settlement.interval_unit]}ごと`} />
+                <MetaRow label="請求タイミング" value={billingTimingLabel} />
+                <MetaRow label="請求日" value={settlement.billing_day ? `毎月${settlement.billing_day}日` : '期首/期末の日付'} />
+                <MetaRow label="御支払条件" value={settlement.payment_terms || '—'} />
+              </tbody>
+            </table>
+            {settlement.sender_company && (
+              <p className="mt-3 text-xs text-neutral-400">
+                {fullAddress({ zip: settlement.sender_zip, pref: settlement.sender_pref, city: settlement.sender_city, address1: settlement.sender_address1, address2: settlement.sender_address2 })}
+              </p>
+            )}
+          </Card>
+
+          {/* 品目 */}
+          <Card className="p-5">
+            <h2 className="mb-4 text-sm font-bold text-neutral-700">品目（1回あたり）</h2>
+            <table className="w-full border-collapse text-sm">
+              <thead>
+                <tr className="bg-primary-50 text-xs text-primary-800">
+                  <th className="border border-neutral-200 px-2 py-2 text-left">品名</th>
+                  <th className="border border-neutral-200 px-2 py-2 text-left">仕様</th>
+                  <th className="border border-neutral-200 px-2 py-2 text-right w-16">数量</th>
+                  <th className="border border-neutral-200 px-2 py-2 text-center w-14">単位</th>
+                  <th className="border border-neutral-200 px-2 py-2 text-right w-24">単価</th>
+                  <th className="border border-neutral-200 px-2 py-2 text-right w-28">金額</th>
+                </tr>
+              </thead>
+              <tbody>
+                {items.map((it, i) => (
+                  <tr key={i}>
+                    <td className="border border-neutral-200 px-2 py-1.5">{it.name}</td>
+                    <td className="border border-neutral-200 px-2 py-1.5 text-neutral-500">{it.spec}</td>
+                    <td className="border border-neutral-200 px-2 py-1.5 text-right">{number(it.quantity)}</td>
+                    <td className="border border-neutral-200 px-2 py-1.5 text-center">{it.unit}</td>
+                    <td className="border border-neutral-200 px-2 py-1.5 text-right">{number(it.unit_price)}</td>
+                    <td className="border border-neutral-200 px-2 py-1.5 text-right font-medium">{number(it.total)}</td>
+                  </tr>
+                ))}
+              </tbody>
+              <tfoot>
+                <tr>
+                  <td colSpan={4} className="border-0"></td>
+                  <td className="border border-neutral-200 px-2 py-1.5 text-right text-neutral-600">小計</td>
+                  <td className="border border-neutral-200 px-2 py-1.5 text-right">{number(subtotal)}</td>
+                </tr>
+                <tr>
+                  <td colSpan={4} className="border-0"></td>
+                  <td className="border border-neutral-200 px-2 py-1.5 text-right text-neutral-600">消費税({taxRate}%)</td>
+                  <td className="border border-neutral-200 px-2 py-1.5 text-right">{number(tax)}</td>
+                </tr>
+                <tr>
+                  <td colSpan={4} className="border-0"></td>
+                  <td className="border border-neutral-200 bg-primary-50 px-2 py-2 text-right font-bold text-primary-800">合計</td>
+                  <td className="border border-neutral-200 bg-primary-50 px-2 py-2 text-right font-bold text-primary-800">{yen(total)}</td>
+                </tr>
+              </tfoot>
+            </table>
+          </Card>
+
+          {/* 備考 */}
+          {settlement.notes && (
+            <Card className="p-5">
+              <div className="text-sm font-medium text-neutral-700">備考：</div>
+              <p className="mt-1 whitespace-pre-wrap text-sm text-neutral-600">{settlement.notes}</p>
+            </Card>
+          )}
+        </div>
+
+        {/* 請求予定 */}
+        <div>
+          <Card className="p-5">
+            <h2 className="mb-4 text-sm font-bold text-neutral-700">請求予定（全{schedules.length}回）</h2>
+            <div className="max-h-[520px] overflow-y-auto">
+              <table className="w-full text-xs">
+                <thead>
+                  <tr className="border-b border-neutral-100 text-left text-neutral-500">
+                    <th className="py-2 pr-2 font-medium">回</th>
+                    <th className="py-2 pr-2 font-medium">対象期間</th>
+                    <th className="py-2 pr-2 font-medium">請求日</th>
+                    <th className="py-2 text-right font-medium">金額</th>
+                  </tr>
+                </thead>
+                <tbody>
+                  {schedules.map((sc) => (
+                    <tr key={sc.id} className="border-b border-neutral-50">
+                      <td className="py-1.5 pr-2 text-neutral-500">{sc.sequence_no}</td>
+                      <td className="py-1.5 pr-2 text-neutral-600">{jpDate(sc.period_start)} 〜 {jpDate(sc.period_end)}</td>
+                      <td className="py-1.5 pr-2 text-neutral-600">{jpDate(sc.billing_date)}</td>
+                      <td className="py-1.5 text-right font-medium text-neutral-800">{yen(sc.total_amount)}</td>
+                    </tr>
+                  ))}
+                </tbody>
+              </table>
+              {schedules.length === 0 && <p className="py-4 text-center text-xs text-neutral-400">請求予定がありません</p>}
+            </div>
+          </Card>
+        </div>
+      </div>
+
+      <Modal
+        open={confirmDelete}
+        onClose={() => setConfirmDelete(false)}
+        title="仕切書を削除しますか？"
+        footer={
+          <>
+            <Button variant="secondary" onClick={() => setConfirmDelete(false)}>キャンセル</Button>
+            <Button variant="danger" onClick={remove}>削除</Button>
+          </>
+        }
+      >
+        <p className="text-sm text-neutral-600">この操作は取り消せません。関連する請求予定もすべて削除されます。</p>
+      </Modal>
+    </div>
+  );
+}
+
+function MetaRow({ label, value }: { label: string; value?: string | null }) {
+  if (!value) return null;
+  return (
+    <tr className="border-b border-neutral-100">
+      <td className="w-32 py-1.5 pr-4 align-top text-neutral-500">{label}</td>
+      <td className="py-1.5 text-neutral-800">{value}</td>
+    </tr>
+  );
+}
diff --git a/resources/js/types.ts b/resources/js/types.ts
index 9599edc..0d8d238 100644
--- a/resources/js/types.ts
+++ b/resources/js/types.ts
@@ -98,6 +98,65 @@ export interface Quote extends SenderSnapshot, CustomerSnapshot {
   updated_at?: string;
 }
 
+// 仕切書（定期性取引のドキュメント）と各回の請求予定データ（issue #54）
+export type SettlementStatus = 'draft' | 'active' | 'ended';
+export type IntervalUnit = 'month' | 'year';
+export type BillingTiming = 'advance' | 'arrears';
+
+export interface Settlement extends SenderSnapshot, CustomerSnapshot {
+  id: ID;
+  // DB は nullable のため、未設定時は null（quote_number と同じ「番号なし下書き」を許容）
+  settlement_number: string | null;
+  subject: string | null;
+  status: SettlementStatus;
+  // 終了条件は end_date か occurrences_count のいずれか必須（無期限は不可）
+  start_date: string;
+  end_date: string | null;
+  occurrences_count: number | null;
+  interval_unit: IntervalUnit;
+  interval_count: number;
+  // 請求日（毎月N日）。月内日数を超える指定は月末にクランプ。null は期境界に従う
+  billing_day: number | null;
+  billing_timing: BillingTiming;
+  payment_terms: string | null;
+  tax_rate: number;
+  notes: string | null;
+  sender_profile_id: ID | '' | null;
+  customer_id: ID | '' | null;
+  // 定期1回あたりの明細・金額（サーバ側で再計算される）。DB は nullable。
+  items: LineItem[] | null;
+  unit_subtotal?: number;
+  unit_tax_amount?: number;
+  unit_total_amount?: number;
+  settlement_schedules?: SettlementSchedule[];
+  created_at?: string;
+  updated_at?: string;
+}
+
+// 各回の請求予定（生成時点の金額・明細スナップショット。実績は持たない）
+export interface SettlementSchedule {
+  id: ID;
+  settlement_id: ID;
+  sequence_no: number;
+  period_start: string;
+  period_end: string;
+  billing_date: string;
+  due_date: string | null;
+  subtotal: number;
+  tax_amount: number;
+  total_amount: number;
+  items: LineItem[] | null;
+  created_at?: string;
+  updated_at?: string;
+}
+
+// GET /api/settlement-schedules のフィルタ（from/to は billing_date に対する範囲）
+export interface SettlementScheduleFilters {
+  settlement_id?: ID;
+  from?: string;
+  to?: string;
+}
+
 // 取込結果（1 ファイル単位）。成功と失敗を判別可能なユニオンで表し、
 // 「quote_id も error も無い」中間状態を型レベルで排除する。
 export interface ImportSuccess {
@@ -136,6 +195,9 @@ export interface BackupPayload {
   customers: Omit<Customer, 'signatures'>[];
   customer_signatures: { id: ID; customer_id: ID; signature: string; created_at?: string; updated_at?: string }[];
   quotes: Quote[];
+  // version 3 で追加（旧バックアップには存在しない）
+  settlements?: Settlement[];
+  settlement_schedules?: SettlementSchedule[];
 }
 
 export interface RestoreResult {
diff --git a/routes/api.php b/routes/api.php
index 2fbc70b..982ea9a 100644
--- a/routes/api.php
+++ b/routes/api.php
@@ -7,6 +7,8 @@
 use App\Http\Controllers\ImportController;
 use App\Http\Controllers\QuoteController;
 use App\Http\Controllers\SenderProfileController;
+use App\Http\Controllers\SettlementController;
+use App\Http\Controllers\SettlementScheduleController;
 use App\Http\Controllers\SetupController;
 use Illuminate\Http\Request;
 use Illuminate\Support\Facades\Artisan;
@@ -33,6 +35,11 @@
     // 御見積書ファイル（xlsx/ods）取込: ファイル名で取引先突合し Quote を生成
     Route::post('quotes/import', [ImportController::class, 'store']);
 
+    // 仕切書と各回の請求予定データ（issue #54 Phase B）
+    Route::apiResource('settlements', SettlementController::class);
+    // 各回の請求予定データを取得（フィルタ: ?settlement_id= / ?from= / ?to=）
+    Route::get('settlement-schedules', [SettlementScheduleController::class, 'index']);
+
     // admin ロール専用: ユーザー管理 CRUD
     Route::middleware('admin')->group(function () {
         Route::apiResource('admin/users', UserController::class)
diff --git a/tests/Feature/BackupTest.php b/tests/Feature/BackupTest.php
index a42a6dd..fd58b5e 100644
--- a/tests/Feature/BackupTest.php
+++ b/tests/Feature/BackupTest.php
@@ -33,8 +33,8 @@ public function test_download_returns_correct_structure(): void
         $res = $this->getJson('/api/backup/download');
 
         $res->assertOk()
-            ->assertJsonStructure(['version', 'exported_at', 'sender_profiles', 'customers', 'customer_signatures', 'quotes'])
-            ->assertJsonPath('version', 2)
+            ->assertJsonStructure(['version', 'exported_at', 'sender_profiles', 'customers', 'customer_signatures', 'quotes', 'settlements', 'settlement_schedules'])
+            ->assertJsonPath('version', 3)
             ->assertJsonCount(1, 'sender_profiles')
             ->assertJsonCount(1, 'customers')
             ->assertJsonCount(1, 'customer_signatures')
@@ -282,7 +282,7 @@ public function test_artisan_export_writes_to_file(): void
         $this->artisan("backup:export --output={$path}")->assertSuccessful();
 
         $data = json_decode(file_get_contents($path), true);
-        $this->assertSame(2, $data['version']);
+        $this->assertSame(3, $data['version']);
 
         unlink($path);
     }
diff --git a/tests/Feature/SettlementApiTest.php b/tests/Feature/SettlementApiTest.php
new file mode 100644
index 0000000..cd9d492
--- /dev/null
+++ b/tests/Feature/SettlementApiTest.php
@@ -0,0 +1,297 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Models\Settlement;
+use App\Models\SettlementSchedule;
+use App\Models\User;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Laravel\Sanctum\Sanctum;
+use Tests\TestCase;
+
+class SettlementApiTest extends TestCase
+{
+    use RefreshDatabase;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        // /api/* は auth:sanctum 配下。CRUD は admin 不要なので一般ユーザーで認証する。
+        Sanctum::actingAs(User::factory()->create());
+    }
+
+    /**
+     * 月次3回・前払（期首請求）の標準的な仕切書 payload。
+     */
+    private function payload(array $overrides = []): array
+    {
+        return array_merge([
+            'settlement_number' => 'S-2026-001',
+            'subject' => 'サーバ保守 月額',
+            'status' => 'active',
+            'start_date' => '2026-01-01',
+            'occurrences_count' => 3,
+            'interval_unit' => 'month',
+            'interval_count' => 1,
+            'billing_timing' => 'advance',
+            'tax_rate' => 10,
+            'items' => [
+                ['name' => '保守費用', 'quantity' => 1, 'unit' => '式', 'unit_price' => 50000],
+            ],
+        ], $overrides);
+    }
+
+    public function test_store_creates_settlement_with_all_schedules(): void
+    {
+        $res = $this->postJson('/api/settlements', $this->payload());
+
+        $res->assertCreated()
+            ->assertJsonPath('settlement_number', 'S-2026-001')
+            ->assertJsonPath('unit_subtotal', 50000)
+            ->assertJsonPath('unit_tax_amount', 5000)
+            ->assertJsonPath('unit_total_amount', 55000)
+            ->assertJsonCount(3, 'settlement_schedules')
+            ->assertJsonPath('settlement_schedules.0.sequence_no', 1)
+            ->assertJsonPath('settlement_schedules.0.billing_date', '2026-01-01')
+            ->assertJsonPath('settlement_schedules.1.billing_date', '2026-02-01')
+            ->assertJsonPath('settlement_schedules.2.billing_date', '2026-03-01')
+            ->assertJsonPath('settlement_schedules.0.total_amount', 55000);
+
+        $this->assertDatabaseCount('settlements', 1);
+        $this->assertDatabaseCount('settlement_schedules', 3);
+    }
+
+    public function test_store_recalculates_amounts_server_side(): void
+    {
+        // クライアントが送る合計金額は信用せず、items からサーバ側で再計算する。
+        $res = $this->postJson('/api/settlements', $this->payload([
+            'items' => [
+                ['name' => '保守費用', 'quantity' => 2, 'unit_price' => 30000, 'total' => 1],
+            ],
+        ]) + ['unit_total_amount' => 1]);
+
+        $res->assertCreated()
+            ->assertJsonPath('items.0.total', 60000)
+            ->assertJsonPath('unit_subtotal', 60000)
+            ->assertJsonPath('unit_tax_amount', 6000)
+            ->assertJsonPath('unit_total_amount', 66000);
+    }
+
+    public function test_store_requires_end_condition(): void
+    {
+        // 終了条件（end_date か occurrences_count）が両方 null なら 422（無期限は不可）。
+        $payload = $this->payload();
+        unset($payload['occurrences_count']);
+
+        $this->postJson('/api/settlements', $payload)
+            ->assertUnprocessable()
+            ->assertJsonValidationErrors(['end_date', 'occurrences_count']);
+    }
+
+    /**
+     * status/interval_count/billing_timing/tax_rate は DB が NOT NULL + default。
+     * 明示的に null を送っても DB エラー(500)にならず 422 で弾かれることを確認する
+     * （レビュー指摘: nullable ルールだと null がそのまま create() に渡り 500 になっていた）。
+     */
+    public function test_explicit_null_on_not_null_columns_returns_422_not_500(): void
+    {
+        foreach (['status', 'interval_count', 'billing_timing', 'tax_rate'] as $field) {
+            $res = $this->postJson('/api/settlements', $this->payload([$field => null]));
+            $res->assertUnprocessable();
+        }
+    }
+
+    /**
+     * ID カラムに配列などの非スカラ値が入ると DB 例外になり得るため、
+     * validation で 422 に落とす。
+     */
+    public function test_relation_ids_reject_non_scalar_values(): void
+    {
+        foreach (['sender_profile_id', 'customer_id'] as $field) {
+            $this->postJson('/api/settlements', $this->payload([$field => ['invalid']]))
+                ->assertUnprocessable()
+                ->assertJsonValidationErrors([$field]);
+        }
+    }
+
+    /**
+     * 上記フィールドを省略した場合は DB default が適用され、正常に作成できる
+     * （sometimes ルールは値が存在する場合のみ検証し、欠落時は create() に渡さない）。
+     */
+    public function test_omitting_not_null_columns_falls_back_to_db_defaults(): void
+    {
+        $payload = $this->payload();
+        unset($payload['status'], $payload['interval_count'], $payload['billing_timing'], $payload['tax_rate']);
+
+        $res = $this->postJson('/api/settlements', $payload);
+
+        $res->assertCreated()
+            ->assertJsonPath('status', 'draft')
+            ->assertJsonPath('interval_count', 1)
+            ->assertJsonPath('billing_timing', 'advance');
+        // tax_rate の DB default は 10。SettlementPricing::apply が明示的に埋めるが、
+        // ここでは default 経路の確認として妥当な値であることのみ検証する。
+        $this->assertSame(10, $res->json('tax_rate'));
+    }
+
+    public function test_settlement_number_must_be_unique_but_null_allows_multiple(): void
+    {
+        $this->postJson('/api/settlements', $this->payload())->assertCreated();
+
+        $this->postJson('/api/settlements', $this->payload())
+            ->assertUnprocessable()
+            ->assertJsonValidationErrors(['settlement_number']);
+
+        // null（番号なし下書き）は UNIQUE の対象外なので複数作成できる。
+        $this->postJson('/api/settlements', $this->payload(['settlement_number' => null]))->assertCreated();
+        $this->postJson('/api/settlements', $this->payload(['settlement_number' => null]))->assertCreated();
+    }
+
+    public function test_update_regenerates_future_schedules_and_keeps_past_snapshots(): void
+    {
+        $id = $this->postJson('/api/settlements', $this->payload())->json('id');
+
+        // 2回目の請求（2026-02-01）まで過去になった時点で単価を改定する。
+        $this->travelTo('2026-02-15');
+        $res = $this->putJson("/api/settlements/{$id}", $this->payload([
+            'items' => [
+                ['name' => '保守費用', 'quantity' => 1, 'unit' => '式', 'unit_price' => 60000],
+            ],
+        ]));
+        $this->travelBack();
+
+        // 過去回（第1回・第2回）はスナップショット不変、未来回（第3回）だけ新単価で再生成。
+        $res->assertOk()
+            ->assertJsonPath('unit_total_amount', 66000)
+            ->assertJsonCount(3, 'settlement_schedules')
+            ->assertJsonPath('settlement_schedules.0.total_amount', 55000)
+            ->assertJsonPath('settlement_schedules.1.total_amount', 55000)
+            ->assertJsonPath('settlement_schedules.2.sequence_no', 3)
+            ->assertJsonPath('settlement_schedules.2.billing_date', '2026-03-01')
+            ->assertJsonPath('settlement_schedules.2.total_amount', 66000);
+    }
+
+    public function test_update_preserves_existing_pricing_inputs_when_omitted(): void
+    {
+        $id = $this->postJson('/api/settlements', $this->payload([
+            'start_date' => '2030-01-01',
+            'tax_rate' => 8,
+        ]))->json('id');
+        $payload = $this->payload([
+            'subject' => '件名のみ更新',
+            'start_date' => '2030-01-01',
+        ]);
+        unset($payload['items'], $payload['tax_rate']);
+
+        $this->putJson("/api/settlements/{$id}", $payload)
+            ->assertOk()
+            ->assertJsonPath('subject', '件名のみ更新')
+            ->assertJsonPath('tax_rate', 8)
+            ->assertJsonPath('items.0.name', '保守費用')
+            ->assertJsonPath('unit_subtotal', 50000)
+            ->assertJsonPath('unit_tax_amount', 4000)
+            ->assertJsonPath('unit_total_amount', 54000)
+            ->assertJsonPath('settlement_schedules.0.total_amount', 54000);
+    }
+
+    public function test_update_rolls_back_settlement_when_schedule_sync_fails(): void
+    {
+        $id = $this->postJson('/api/settlements', $this->payload([
+            'start_date' => '2030-01-01',
+        ]))->json('id');
+
+        SettlementSchedule::creating(function (): void {
+            throw new \RuntimeException('schedule sync failed');
+        });
+        $this->withoutExceptionHandling();
+
+        try {
+            $this->putJson("/api/settlements/{$id}", $this->payload([
+                'subject' => '更新後の件名',
+                'start_date' => '2030-01-01',
+            ]));
+            $this->fail('schedule sync failure was not thrown');
+        } catch (\RuntimeException $e) {
+            $this->assertSame('schedule sync failed', $e->getMessage());
+        }
+
+        $this->assertSame('サーバ保守 月額', Settlement::findOrFail($id)->subject);
+        $this->assertDatabaseCount('settlement_schedules', 3);
+    }
+
+    public function test_show_and_destroy(): void
+    {
+        $id = $this->postJson('/api/settlements', $this->payload())->json('id');
+
+        $this->getJson("/api/settlements/{$id}")
+            ->assertOk()
+            ->assertJsonPath('id', $id)
+            ->assertJsonCount(3, 'settlement_schedules');
+
+        $this->deleteJson("/api/settlements/{$id}")->assertNoContent();
+
+        // 親削除で各回も cascade 削除される。
+        $this->assertDatabaseCount('settlements', 0);
+        $this->assertDatabaseCount('settlement_schedules', 0);
+    }
+
+    public function test_index_returns_settlements_with_schedules(): void
+    {
+        $this->postJson('/api/settlements', $this->payload())->assertCreated();
+        $this->postJson('/api/settlements', $this->payload([
+            'settlement_number' => 'S-2026-002',
+            'start_date' => '2026-04-01',
+        ]))->assertCreated();
+
+        $this->getJson('/api/settlements')
+            ->assertOk()
+            ->assertJsonCount(2)
+            // start_date 降順
+            ->assertJsonPath('0.settlement_number', 'S-2026-002')
+            ->assertJsonCount(3, '0.settlement_schedules');
+    }
+
+    public function test_schedules_index_returns_and_filters_schedules(): void
+    {
+        $monthlyId = $this->postJson('/api/settlements', $this->payload())->json('id');
+        $this->postJson('/api/settlements', $this->payload([
+            'settlement_number' => 'S-2026-002',
+            'start_date' => '2026-01-10',
+            'occurrences_count' => 2,
+            'interval_unit' => 'year',
+        ]))->assertCreated();
+
+        // フィルタなし: 月次3回 + 年次2回 = 5件、billing_date 昇順。
+        $this->getJson('/api/settlement-schedules')
+            ->assertOk()
+            ->assertJsonCount(5)
+            ->assertJsonPath('0.billing_date', '2026-01-01');
+
+        // settlement_id で絞り込み。
+        $this->getJson("/api/settlement-schedules?settlement_id={$monthlyId}")
+            ->assertOk()
+            ->assertJsonCount(3);
+
+        // 0 も整数フィルタとして適用し、フィルタなしの全件取得にしない。
+        $this->getJson('/api/settlement-schedules?settlement_id=0')
+            ->assertOk()
+            ->assertJsonCount(0);
+
+        // from/to は billing_date に対する範囲（年次の2回目 2027-01-10 は範囲外）。
+        $this->getJson('/api/settlement-schedules?from=2026-02-01&to=2026-12-31')
+            ->assertOk()
+            ->assertJsonCount(2)
+            ->assertJsonPath('0.billing_date', '2026-02-01')
+            ->assertJsonPath('1.billing_date', '2026-03-01');
+    }
+
+    public function test_quotes_api_is_unaffected(): void
+    {
+        // 回帰: settlements 追加後も quotes API は従来どおり動く。
+        $this->postJson('/api/settlements', $this->payload())->assertCreated();
+
+        $this->postJson('/api/quotes', ['subject' => '回帰確認'])->assertCreated();
+        $this->getJson('/api/quotes')->assertOk()->assertJsonCount(1);
+    }
+}
diff --git a/tests/Feature/SettlementBackupTest.php b/tests/Feature/SettlementBackupTest.php
new file mode 100644
index 0000000..9bc52c4
--- /dev/null
+++ b/tests/Feature/SettlementBackupTest.php
@@ -0,0 +1,298 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Models\Settlement;
+use App\Models\SettlementSchedule;
+use App\Models\User;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Http\UploadedFile;
+use Illuminate\Testing\TestResponse;
+use Tests\TestCase;
+
+class SettlementBackupTest extends TestCase
+{
+    use RefreshDatabase;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->actingAs(User::factory()->create(['role' => 'admin']));
+    }
+
+    public function test_download_includes_settlements_and_schedules(): void
+    {
+        $settlement = Settlement::create([
+            'settlement_number' => 'S-001',
+            'start_date' => '2026-01-01',
+            'occurrences_count' => 1,
+            'interval_unit' => 'month',
+            'items' => [['name' => '保守費用']],
+        ]);
+        $settlement->settlementSchedules()->create([
+            'sequence_no' => 1,
+            'period_start' => '2026-01-01',
+            'period_end' => '2026-01-31',
+            'billing_date' => '2026-01-01',
+            'items' => [['name' => '保守費用']],
+        ]);
+
+        $this->getJson('/api/backup/download')
+            ->assertOk()
+            ->assertJsonCount(1, 'settlements')
+            ->assertJsonCount(1, 'settlement_schedules')
+            ->assertJsonPath('settlements.0.settlement_number', 'S-001')
+            ->assertJsonPath('settlements.0.items.0.name', '保守費用')
+            ->assertJsonPath('settlement_schedules.0.sequence_no', 1);
+    }
+
+    public function test_restore_inserts_settlements_and_schedules(): void
+    {
+        $payload = $this->makeBackup(
+            settlements: [[
+                'id' => 1, 'settlement_number' => 'S-001', 'start_date' => '2026-01-01',
+                'occurrences_count' => 1, 'interval_unit' => 'month',
+                'items' => [['name' => '保守費用', 'quantity' => 1, 'unit_price' => 50000, 'total' => 50000]],
+                'created_at' => now(), 'updated_at' => now(),
+            ]],
+            settlementSchedules: [[
+                'id' => 1, 'settlement_id' => 1, 'sequence_no' => 1,
+                'period_start' => '2026-01-01', 'period_end' => '2026-01-31', 'billing_date' => '2026-01-01',
+                'items' => [['name' => '保守費用', 'quantity' => 1, 'unit_price' => 50000, 'total' => 50000]],
+                'created_at' => now(), 'updated_at' => now(),
+            ]],
+        );
+
+        $this->postRestore($payload)
+            ->assertOk()
+            ->assertJsonPath('inserted', 2)
+            ->assertJsonPath('errors', []);
+
+        $this->assertDatabaseHas('settlements', ['settlement_number' => 'S-001']);
+        $this->assertDatabaseHas('settlement_schedules', ['settlement_id' => 1, 'sequence_no' => 1]);
+        // items は JSON 文字列として保存され、model cast で配列に戻る。
+        $this->assertSame('保守費用', SettlementSchedule::first()->items[0]['name']);
+    }
+
+    /**
+     * json_decode は数値を int/string どちらにもデコードし得る（バックアップファイルの
+     * 手動編集や別ツール生成では特に）。settlement の id が文字列、schedule 側の
+     * settlement_id が数値のように型が食い違っても、親子の紐付けが skip されないことを確認する
+     * （レビュー指摘: 型不一致で in_array の strict 比較が全滅する不具合の回帰テスト）。
+     */
+    public function test_restore_links_schedule_to_settlement_even_with_mismatched_id_types(): void
+    {
+        $payload = $this->makeBackup(
+            settlements: [[
+                'id' => '1', 'settlement_number' => 'S-TYPE', 'start_date' => '2026-01-01',
+                'occurrences_count' => 1, 'interval_unit' => 'month',
+                'created_at' => now(), 'updated_at' => now(),
+            ]],
+            settlementSchedules: [[
+                'id' => 1, 'settlement_id' => 1, 'sequence_no' => 1,
+                'period_start' => '2026-01-01', 'period_end' => '2026-01-31', 'billing_date' => '2026-01-01',
+                'created_at' => now(), 'updated_at' => now(),
+            ]],
+        );
+
+        $this->postRestore($payload)
+            ->assertOk()
+            ->assertJsonPath('inserted', 2)
+            ->assertJsonPath('skipped', 0);
+
+        $this->assertDatabaseHas('settlement_schedules', ['settlement_id' => 1, 'sequence_no' => 1]);
+    }
+
+    public function test_restore_skip_does_not_link_schedules_to_existing_settlement(): void
+    {
+        $existing = Settlement::create([
+            'settlement_number' => 'S-EXISTING',
+            'start_date' => '2026-01-01',
+            'occurrences_count' => 1,
+            'interval_unit' => 'month',
+        ]);
+
+        // skip モードでは既存 id の仕切書は上書きされず、その予定も別仕切書へ紐付けない。
+        $payload = $this->makeBackup(
+            settlements: [[
+                'id' => $existing->id, 'settlement_number' => 'S-RESTORED', 'start_date' => '2026-02-01',
+                'occurrences_count' => 1, 'interval_unit' => 'month',
+                'created_at' => now(), 'updated_at' => now(),
+            ]],
+            settlementSchedules: [[
+                'id' => 1, 'settlement_id' => $existing->id, 'sequence_no' => 1,
+                'period_start' => '2026-02-01', 'period_end' => '2026-02-28', 'billing_date' => '2026-02-01',
+                'created_at' => now(), 'updated_at' => now(),
+            ]],
+        );
+
+        $this->postRestore($payload)
+            ->assertOk()
+            ->assertJsonPath('inserted', 0)
+            ->assertJsonPath('skipped', 2);
+
+        $this->assertDatabaseHas('settlements', ['settlement_number' => 'S-EXISTING']);
+        $this->assertDatabaseCount('settlement_schedules', 0);
+    }
+
+    public function test_restore_overwrite_updates_settlement_and_relinks_schedules(): void
+    {
+        $existing = Settlement::create([
+            'settlement_number' => 'S-OLD',
+            'start_date' => '2026-01-01',
+            'occurrences_count' => 1,
+            'interval_unit' => 'month',
+        ]);
+
+        $payload = $this->makeBackup(
+            settlements: [[
+                'id' => $existing->id, 'settlement_number' => 'S-NEW', 'start_date' => '2026-01-01',
+                'occurrences_count' => 1, 'interval_unit' => 'month',
+                'created_at' => now(), 'updated_at' => now(),
+            ]],
+            settlementSchedules: [[
+                'id' => 1, 'settlement_id' => $existing->id, 'sequence_no' => 1,
+                'period_start' => '2026-01-01', 'period_end' => '2026-01-31', 'billing_date' => '2026-01-01',
+                'created_at' => now(), 'updated_at' => now(),
+            ]],
+        );
+
+        $this->postRestore($payload, 'overwrite')
+            ->assertOk()
+            ->assertJsonPath('updated', 1)
+            ->assertJsonPath('inserted', 1);
+
+        $this->assertDatabaseHas('settlements', ['settlement_number' => 'S-NEW']);
+        $this->assertDatabaseHas('settlement_schedules', ['settlement_id' => $existing->id]);
+    }
+
+    public function test_restore_rejects_schedule_missing_required_columns(): void
+    {
+        // billing_date 欠落は DB の NOT NULL 違反（500）になる前に 422 で拒否する。
+        $payload = $this->makeBackup(settlementSchedules: [[
+            'id' => 1, 'settlement_id' => 1, 'sequence_no' => 1,
+            'period_start' => '2026-01-01', 'period_end' => '2026-01-31',
+        ]]);
+
+        $this->postRestore($payload)->assertUnprocessable();
+    }
+
+    /**
+     * billing_date 等が「値としては存在するが不正な形式」の場合、DB保存後の date cast 読み出し時に
+     * 例外化する（500）前に 422 で拒否する（レビュー指摘: 値域検証が欠落していた回帰テスト）。
+     */
+    public function test_restore_rejects_settlement_schedule_with_invalid_column_values(): void
+    {
+        $base = [
+            'id' => 1, 'settlement_id' => 1, 'sequence_no' => 1,
+            'period_start' => '2026-01-01', 'period_end' => '2026-01-31', 'billing_date' => '2026-01-01',
+        ];
+        $invalidValues = [
+            ['billing_date' => 'not-a-date'],
+            ['period_end' => '2025-12-01'], // period_start より前
+            ['sequence_no' => 0],
+            ['settlement_id' => 'abc'],
+        ];
+
+        foreach ($invalidValues as $invalidValue) {
+            $payload = $this->makeBackup(
+                settlements: [['id' => 1, 'start_date' => '2026-01-01', 'occurrences_count' => 1, 'interval_unit' => 'month']],
+                settlementSchedules: [array_merge($base, $invalidValue)],
+            );
+
+            $this->postRestore($payload)->assertUnprocessable();
+        }
+    }
+
+    public function test_restore_rejects_null_settlement_default_column(): void
+    {
+        $payload = $this->makeBackup(settlements: [[
+            'id' => 1, 'status' => null, 'start_date' => '2026-01-01',
+            'interval_unit' => 'month', 'interval_count' => 1, 'billing_timing' => 'advance',
+            'tax_rate' => 10, 'unit_subtotal' => 0, 'unit_tax_amount' => 0, 'unit_total_amount' => 0,
+        ]]);
+
+        $this->postRestore($payload)->assertUnprocessable();
+    }
+
+    public function test_restore_rejects_settlement_without_end_condition(): void
+    {
+        $payload = $this->makeBackup(settlements: [[
+            'id' => 1, 'start_date' => '2026-01-01', 'interval_unit' => 'month',
+            'end_date' => null, 'occurrences_count' => null,
+        ]]);
+
+        $this->postRestore($payload)->assertUnprocessable();
+    }
+
+    public function test_restore_rejects_invalid_settlement_schedule_conditions(): void
+    {
+        $invalidValues = [
+            ['interval_unit' => 'foo'],
+            ['interval_count' => 0],
+            ['billing_day' => []],
+            ['occurrences_count' => 0],
+        ];
+
+        foreach ($invalidValues as $invalidValue) {
+            $settlement = array_merge([
+                'id' => 1, 'start_date' => '2026-01-01', 'occurrences_count' => 1,
+                'interval_unit' => 'month',
+            ], $invalidValue);
+
+            $this->postRestore($this->makeBackup(settlements: [$settlement]))
+                ->assertUnprocessable();
+        }
+    }
+
+    public function test_restore_rejects_null_schedule_default_column(): void
+    {
+        $payload = $this->makeBackup(settlementSchedules: [[
+            'id' => 1, 'settlement_id' => 1, 'sequence_no' => 1,
+            'period_start' => '2026-01-01', 'period_end' => '2026-01-31', 'billing_date' => '2026-01-01',
+            'subtotal' => null, 'tax_amount' => 0, 'total_amount' => 0,
+        ]]);
+
+        $this->postRestore($payload)->assertUnprocessable();
+    }
+
+    public function test_restore_of_version_two_backup_without_settlements_still_works(): void
+    {
+        // 旧 version 2 バックアップ（settlements キーなし）も従来どおり復元できる。
+        $payload = json_encode([
+            'version' => 2,
+            'exported_at' => now()->toIso8601String(),
+            'sender_profiles' => [],
+            'customers' => [['id' => 1, 'customer_name' => '旧形式商事', 'created_at' => now(), 'updated_at' => now()]],
+            'customer_signatures' => [],
+            'quotes' => [],
+        ]);
+
+        $this->postRestore($payload)->assertOk()->assertJsonPath('inserted', 1);
+        $this->assertDatabaseHas('customers', ['customer_name' => '旧形式商事']);
+    }
+
+    // ---------- ヘルパー ----------
+
+    private function makeBackup(array $settlements = [], array $settlementSchedules = []): string
+    {
+        return json_encode([
+            'version' => 3,
+            'exported_at' => now()->toIso8601String(),
+            'sender_profiles' => [],
+            'customers' => [],
+            'customer_signatures' => [],
+            'quotes' => [],
+            'settlements' => $settlements,
+            'settlement_schedules' => $settlementSchedules,
+        ]);
+    }
+
+    /** multipart/form-data で /api/backup/restore を呼ぶ */
+    private function postRestore(string $payload, string $mode = 'skip'): TestResponse
+    {
+        $file = UploadedFile::fake()->createWithContent('backup.json', $payload);
+
+        return $this->call('POST', '/api/backup/restore', ['mode' => $mode], [], ['file' => $file], ['Accept' => 'application/json']);
+    }
+}
diff --git a/tests/Feature/SettlementScheduleGeneratorTest.php b/tests/Feature/SettlementScheduleGeneratorTest.php
new file mode 100644
index 0000000..944e3b7
--- /dev/null
+++ b/tests/Feature/SettlementScheduleGeneratorTest.php
@@ -0,0 +1,280 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Models\Settlement;
+use App\Models\SettlementSchedule;
+use App\Support\SettlementPricing;
+use App\Support\SettlementScheduleGenerator;
+use Carbon\CarbonImmutable;
+use Illuminate\Database\UniqueConstraintViolationException;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use InvalidArgumentException;
+use Tests\TestCase;
+
+class SettlementScheduleGeneratorTest extends TestCase
+{
+    use RefreshDatabase;
+
+    public function test_models_cast_values_and_define_relations(): void
+    {
+        $settlement = $this->settlement([
+            'items' => [['name' => '保守']],
+            'start_date' => '2024-01-01',
+            'end_date' => '2024-01-31',
+        ]);
+        $schedule = $settlement->settlementSchedules()->create([
+            'sequence_no' => 1,
+            'period_start' => '2024-01-01',
+            'period_end' => '2024-01-31',
+            'billing_date' => '2024-01-01',
+            'subtotal' => 100,
+            'tax_amount' => 10,
+            'total_amount' => 110,
+            'items' => [['name' => '保守']],
+        ]);
+
+        $this->assertSame('2024-01-01', $settlement->start_date->format('Y-m-d'));
+        $this->assertSame([['name' => '保守']], $schedule->items);
+        $this->assertTrue($schedule->settlement->is($settlement));
+        $this->assertTrue($settlement->settlementSchedules->first()->is($schedule));
+    }
+
+    public function test_settlement_number_is_nullable_and_unique(): void
+    {
+        $this->settlement(['settlement_number' => null]);
+        $this->settlement(['settlement_number' => null]);
+        $this->settlement(['settlement_number' => 'S-001']);
+
+        $this->expectException(UniqueConstraintViolationException::class);
+        $this->settlement(['settlement_number' => 'S-001']);
+    }
+
+    public function test_schedule_sequence_is_unique_per_settlement_and_cascades_on_delete(): void
+    {
+        $settlement = $this->settlement();
+        $attributes = [
+            'sequence_no' => 1,
+            'period_start' => '2024-01-01',
+            'period_end' => '2024-01-31',
+            'billing_date' => '2024-01-01',
+        ];
+        $schedule = $settlement->settlementSchedules()->create($attributes);
+
+        $otherSettlement = $this->settlement();
+        $otherSettlement->settlementSchedules()->create($attributes);
+        $settlement->delete();
+
+        $this->assertDatabaseMissing('settlement_schedules', ['id' => $schedule->id]);
+
+        $duplicateSettlement = $this->settlement();
+        $duplicateSettlement->settlementSchedules()->create($attributes);
+        $this->expectException(UniqueConstraintViolationException::class);
+        $duplicateSettlement->settlementSchedules()->create($attributes);
+    }
+
+    public function test_settlement_schedules_relation_is_ordered_by_sequence_number(): void
+    {
+        $settlement = $this->settlement();
+        $attributes = [
+            'period_start' => '2024-01-01',
+            'period_end' => '2024-01-31',
+            'billing_date' => '2024-01-01',
+        ];
+
+        $settlement->settlementSchedules()->create($attributes + ['sequence_no' => 2]);
+        $settlement->settlementSchedules()->create($attributes + ['sequence_no' => 1]);
+
+        $this->assertSame([1, 2], $settlement->settlementSchedules->pluck('sequence_no')->all());
+    }
+
+    public function test_generates_monthly_periods_from_month_end_and_clamps_billing_day(): void
+    {
+        $settlement = $this->settlement([
+            'start_date' => '2024-01-31',
+            'occurrences_count' => 3,
+            'billing_day' => 31,
+        ]);
+
+        $schedules = SettlementScheduleGenerator::generate($settlement);
+
+        $this->assertSame(
+            ['2024-01-31', '2024-02-29', '2024-03-31'],
+            array_column($schedules, 'period_start'),
+        );
+        $this->assertSame(
+            ['2024-02-28', '2024-03-30', '2024-04-29'],
+            array_column($schedules, 'period_end'),
+        );
+        $this->assertSame(
+            ['2024-01-31', '2024-02-29', '2024-03-31'],
+            array_column($schedules, 'billing_date'),
+        );
+    }
+
+    public function test_supports_multi_month_arrears_periods(): void
+    {
+        $settlement = $this->settlement([
+            'start_date' => '2024-01-15',
+            'occurrences_count' => 3,
+            'interval_count' => 2,
+            'billing_timing' => 'arrears',
+        ]);
+
+        $schedules = SettlementScheduleGenerator::generate($settlement);
+
+        $this->assertSame(
+            ['2024-03-14', '2024-05-14', '2024-07-14'],
+            array_column($schedules, 'billing_date'),
+        );
+    }
+
+    public function test_supports_yearly_intervals_and_leap_day_clamping(): void
+    {
+        $settlement = $this->settlement([
+            'start_date' => '2024-02-29',
+            'occurrences_count' => 3,
+            'interval_unit' => 'year',
+            'interval_count' => 2,
+            'billing_day' => 31,
+        ]);
+
+        $schedules = SettlementScheduleGenerator::generate($settlement);
+
+        $this->assertSame(
+            ['2024-02-29', '2026-02-28', '2028-02-29'],
+            array_column($schedules, 'period_start'),
+        );
+        $this->assertSame(
+            ['2024-02-29', '2026-02-28', '2028-02-29'],
+            array_column($schedules, 'billing_date'),
+        );
+    }
+
+    public function test_stops_at_whichever_boundary_is_reached_first(): void
+    {
+        $settlement = $this->settlement([
+            'start_date' => '2024-01-01',
+            'end_date' => '2024-03-15',
+            'occurrences_count' => 12,
+        ]);
+
+        $schedules = SettlementScheduleGenerator::generate($settlement);
+
+        $this->assertCount(3, $schedules);
+        $this->assertSame('2024-03-15', $schedules[2]['period_end']);
+
+        $settlement->end_date = '2025-12-31';
+        $settlement->occurrences_count = 2;
+
+        $this->assertCount(2, SettlementScheduleGenerator::generate($settlement));
+    }
+
+    public function test_end_date_alone_creates_a_finite_partial_final_period(): void
+    {
+        $settlement = $this->settlement([
+            'start_date' => '2024-01-15',
+            'end_date' => '2024-03-20',
+            'occurrences_count' => null,
+        ]);
+
+        $schedules = SettlementScheduleGenerator::generate($settlement);
+
+        $this->assertCount(3, $schedules);
+        $this->assertSame('2024-03-15', $schedules[2]['period_start']);
+        $this->assertSame('2024-03-20', $schedules[2]['period_end']);
+    }
+
+    public function test_each_schedule_snapshots_items_and_per_occurrence_amounts(): void
+    {
+        $priced = SettlementPricing::apply([
+            'tax_rate' => 10,
+            'items' => [['name' => '月額保守', 'quantity' => 1, 'unit_price' => 105]],
+        ]);
+        $settlement = $this->settlement($priced + ['occurrences_count' => 2]);
+
+        $schedules = SettlementScheduleGenerator::generate($settlement);
+
+        $this->assertSame(105, $schedules[0]['subtotal']);
+        $this->assertSame(10, $schedules[0]['tax_amount']);
+        $this->assertSame(115, $schedules[0]['total_amount']);
+        $this->assertSame('月額保守', $schedules[1]['items'][0]['name']);
+    }
+
+    public function test_sync_preserves_past_snapshot_and_replaces_future_schedules(): void
+    {
+        $settlement = $this->settlement([
+            'start_date' => '2024-01-01',
+            'occurrences_count' => 3,
+            'items' => [['name' => '旧明細']],
+            'unit_subtotal' => 100,
+            'unit_tax_amount' => 10,
+            'unit_total_amount' => 110,
+        ]);
+        SettlementScheduleGenerator::sync($settlement, CarbonImmutable::parse('2024-01-01'));
+        $past = SettlementSchedule::where('sequence_no', 1)->firstOrFail();
+
+        $settlement->update([
+            'items' => [['name' => '新明細']],
+            'unit_subtotal' => 200,
+            'unit_tax_amount' => 20,
+            'unit_total_amount' => 220,
+        ]);
+        SettlementScheduleGenerator::sync($settlement->fresh(), CarbonImmutable::parse('2024-02-01'));
+
+        $this->assertSame(3, $settlement->settlementSchedules()->count());
+        $this->assertSame($past->id, SettlementSchedule::where('sequence_no', 1)->value('id'));
+        $this->assertSame('旧明細', SettlementSchedule::where('sequence_no', 1)->firstOrFail()->items[0]['name']);
+        $this->assertSame(220, SettlementSchedule::where('sequence_no', 2)->value('total_amount'));
+        $this->assertSame('新明細', SettlementSchedule::where('sequence_no', 3)->firstOrFail()->items[0]['name']);
+    }
+
+    public function test_sync_recreates_future_sequence_even_when_new_billing_date_moves_before_cutoff(): void
+    {
+        $settlement = $this->settlement([
+            'start_date' => '2024-01-01',
+            'occurrences_count' => 3,
+            'billing_timing' => 'arrears',
+        ]);
+        SettlementScheduleGenerator::sync($settlement, CarbonImmutable::parse('2024-01-01'));
+        $past = SettlementSchedule::where('sequence_no', 1)->firstOrFail();
+
+        $settlement->update(['billing_timing' => 'advance']);
+        SettlementScheduleGenerator::sync($settlement->fresh(), CarbonImmutable::parse('2024-02-15'));
+
+        $schedules = $settlement->settlementSchedules()->get();
+        $this->assertSame(3, $schedules->count());
+        $this->assertSame($past->id, $schedules->firstWhere('sequence_no', 1)->id);
+        $this->assertSame(
+            ['2024-01-31', '2024-02-01', '2024-03-01'],
+            $schedules->pluck('billing_date')->map->format('Y-m-d')->all(),
+        );
+    }
+
+    public function test_requires_a_finite_valid_schedule(): void
+    {
+        $settlement = $this->settlement(['end_date' => null, 'occurrences_count' => null]);
+
+        $this->expectException(InvalidArgumentException::class);
+        SettlementScheduleGenerator::generate($settlement);
+    }
+
+    private function settlement(array $attributes = []): Settlement
+    {
+        return Settlement::create(array_merge([
+            'status' => 'draft',
+            'start_date' => '2024-01-01',
+            'end_date' => null,
+            'occurrences_count' => 1,
+            'interval_unit' => 'month',
+            'interval_count' => 1,
+            'billing_day' => null,
+            'billing_timing' => 'advance',
+            'tax_rate' => 10,
+            'items' => [],
+            'unit_subtotal' => 0,
+            'unit_tax_amount' => 0,
+            'unit_total_amount' => 0,
+        ], $attributes));
+    }
+}
diff --git a/tests/Unit/SettlementPricingTest.php b/tests/Unit/SettlementPricingTest.php
new file mode 100644
index 0000000..675c042
--- /dev/null
+++ b/tests/Unit/SettlementPricingTest.php
@@ -0,0 +1,38 @@
+<?php
+
+namespace Tests\Unit;
+
+use App\Support\SettlementPricing;
+use PHPUnit\Framework\TestCase;
+
+class SettlementPricingTest extends TestCase
+{
+    public function test_apply_recalculates_each_item_and_unit_totals(): void
+    {
+        $result = SettlementPricing::apply([
+            'tax_rate' => 10,
+            'unit_total_amount' => 999999,
+            'items' => [
+                ['name' => '商品A', 'quantity' => 3, 'unit_price' => 1000, 'total' => 1],
+                ['name' => '商品B', 'quantity' => 2, 'unit_price' => 500, 'total' => 1],
+            ],
+        ]);
+
+        $this->assertSame(3000, $result['items'][0]['total']);
+        $this->assertSame(1000, $result['items'][1]['total']);
+        $this->assertSame(4000, $result['unit_subtotal']);
+        $this->assertSame(400, $result['unit_tax_amount']);
+        $this->assertSame(4400, $result['unit_total_amount']);
+    }
+
+    public function test_tax_is_floored_for_one_occurrence(): void
+    {
+        $result = SettlementPricing::apply([
+            'tax_rate' => 10,
+            'items' => [['quantity' => 1, 'unit_price' => 105]],
+        ]);
+
+        $this->assertSame(10, $result['unit_tax_amount']);
+        $this->assertSame(115, $result['unit_total_amount']);
+    }
+}
diff --git a/tests/e2e/settlements.spec.js b/tests/e2e/settlements.spec.js
new file mode 100644
index 0000000..a792c6f
--- /dev/null
+++ b/tests/e2e/settlements.spec.js
@@ -0,0 +1,87 @@
+import { test, expect } from './fixtures';
+import { login } from './helpers';
+
+test.beforeEach(async ({ page }) => {
+  await login(page);
+});
+
+test.describe('仕切書', () => {
+  test('見積書一覧のスイッチをONにすると仕切書作成へ遷移する', async ({ page }) => {
+    await page.getByRole('switch', { name: '仕切書として作成' }).click();
+    await page.getByRole('button', { name: '新規作成' }).click();
+    await expect(page).toHaveURL(/\/settlements\/new$/);
+  });
+
+  test('一覧は空状態から開始する', async ({ page }) => {
+    await page.goto('/settlements');
+    await expect(page.getByText('仕切書がありません')).toBeVisible();
+  });
+
+  test('新規作成: 取引先・期間・品目を入力して保存できる（請求予定が生成される）', async ({ page }) => {
+    await page.goto('/settlements/new');
+
+    await page.getByLabel('取引先').selectOption({ label: '株式会社アルファ商事' });
+
+    await page.getByLabel('開始日').fill('2026-01-01');
+    // 終了条件: 回数指定に切り替えて 3 回
+    await page.getByLabel('終了条件の種類').selectOption('count');
+    await page.getByPlaceholder('回数').fill('3');
+
+    const row = page.locator('.grid.grid-cols-12').nth(1);
+    await row.locator('input').nth(0).fill('保守サービス');
+    await row.locator('input[type=number]').nth(0).fill('1');
+    await row.locator('input[type=number]').nth(2).fill('50000');
+
+    await expect(page.getByText('¥55,000')).toBeVisible();
+
+    await page.getByRole('button', { name: '保存' }).click();
+    await expect(page).toHaveURL(/\/settlements\/[^/]+$/);
+    await expect(page.getByText('請求予定（全3回）')).toBeVisible();
+
+    await page.goto('/settlements');
+    await expect(page.locator('tbody tr')).toHaveCount(1);
+    await expect(page.locator('tbody').getByText('株式会社アルファ商事')).toBeVisible();
+  });
+
+  test('既存仕切書を編集してステータスを変更できる', async ({ page }) => {
+    await page.goto('/settlements/new');
+    await page.getByLabel('取引先').selectOption({ label: 'ベータ工業株式会社' });
+    await page.getByLabel('開始日').fill('2026-01-01');
+    await page.getByLabel('終了条件の種類').selectOption('count');
+    await page.getByPlaceholder('回数').fill('2');
+    const row = page.locator('.grid.grid-cols-12').nth(1);
+    await row.locator('input').nth(0).fill('定期納品');
+    await row.locator('input[type=number]').nth(0).fill('1');
+    await row.locator('input[type=number]').nth(2).fill('10000');
+    await page.getByRole('button', { name: '保存' }).click();
+    await expect(page).toHaveURL(/\/settlements\/[^/]+$/);
+
+    await page.getByRole('button', { name: '編集' }).click();
+    await expect(page).toHaveURL(/\/settlements\/[^/]+\/edit$/);
+    await page.getByLabel('ステータス').selectOption('active');
+    await page.getByRole('button', { name: '保存' }).click();
+
+    await expect(page).toHaveURL(/\/settlements\/[^/]+$/);
+    await expect(page.getByText('契約中')).toBeVisible();
+  });
+
+  test('仕切書を削除できる（確認モーダル経由）', async ({ page }) => {
+    await page.goto('/settlements/new');
+    await page.getByLabel('取引先').selectOption({ label: 'ベータ工業株式会社' });
+    await page.getByLabel('開始日').fill('2026-01-01');
+    await page.getByLabel('終了条件の種類').selectOption('count');
+    await page.getByPlaceholder('回数').fill('1');
+    const row = page.locator('.grid.grid-cols-12').nth(1);
+    await row.locator('input').nth(0).fill('削除確認用');
+    await row.locator('input[type=number]').nth(0).fill('1');
+    await row.locator('input[type=number]').nth(2).fill('1000');
+    await page.getByRole('button', { name: '保存' }).click();
+    await expect(page).toHaveURL(/\/settlements\/[^/]+$/);
+
+    await page.getByRole('button', { name: '削除' }).click();
+    await expect(page.getByText('この操作は取り消せません。')).toBeVisible();
+    await page.getByRole('button', { name: '削除', exact: true }).last().click();
+    await expect(page).toHaveURL(/\/settlements$/);
+    await expect(page.getByText('仕切書がありません')).toBeVisible();
+  });
+});