diff --git a/src/orcid-account/orcidAccountResolvers.ts b/src/orcid-account/orcidAccountResolvers.ts
index 86613d3..a596478 100644
--- a/src/orcid-account/orcidAccountResolvers.ts
+++ b/src/orcid-account/orcidAccountResolvers.ts
@@ -73,7 +73,7 @@ const orcidAccountResolvers = {
     ): Promise<ResolverOrcidAccount | null> => {
       if (!isOrcidId(id)) {
         throw new Error(
-          `Invalid ORCID identifier: '${id}'. Expected format: 0000-0000-0000-000X`,
+          `Invalid ORCID identifier: '${id}'. See https://support.orcid.org/hc/en-us/articles/360006897674-Structure-of-the-ORCID-Identifier.`,
         );
       }
 
diff --git a/src/utils/assert.ts b/src/utils/assert.ts
index b6b7faf..f823d08 100644
--- a/src/utils/assert.ts
+++ b/src/utils/assert.ts
@@ -293,9 +293,53 @@ export function isAccountId(id: string): boolean {
   );
 }
 
-// ORCID
-export function isOrcidId(id: string): boolean {
-  // ORCID ID format: 0000-0000-0000-000X where X can be 0-9 or X
-  const orcidPattern = /^\d{4}-\d{4}-\d{4}-\d{3}[\dX]$/;
-  return orcidPattern.test(id);
+/**
+ * Validates an ORCID iD.
+ *
+ * An ORCID iD is a 16-character string that follows a specific structure:
+ * - It consists of 15 digits followed by a check digit (0-9 or 'X').
+ * - It is often formatted with hyphens, e.g., "0000-0002-1825-0097".
+ * - The validation uses the ISO 7064 11,2 checksum algorithm.
+ *
+ * @param {string} orcid The ORCID iD string to validate.
+ * @returns {boolean} True if the ORCID iD is valid, false otherwise.
+ */
+export function isOrcidId(orcidId: string): boolean {
+  if (typeof orcidId !== 'string') {
+    return false;
+  }
+
+  // Remove hyphens and whitespace to get the base 16 characters.
+  const baseStr: string = orcidId.replace(/[-\s]/g, '');
+
+  // An ORCID must be 16 characters long and match the pattern:
+  // 15 digits followed by a final character that is a digit or 'X'.
+  const orcidPattern: RegExp = /^\d{15}[\dX]$/;
+  if (!orcidPattern.test(baseStr.toUpperCase())) {
+    return false;
+  }
+
+  // --- Checksum Calculation (ISO 7064 11,2) ---
+
+  let total: number = 0;
+  // Iterate over the first 15 digits of the ORCID.
+  for (let i = 0; i < 15; i++) {
+    const digit: number = parseInt(baseStr[i], 10);
+    total = (total + digit) * 2;
+  }
+
+  // Calculate the remainder when divided by 11.
+  const remainder: number = total % 11;
+  // Subtract the remainder from 12.
+  const result: number = (12 - remainder) % 11;
+
+  // Determine the correct check digit from the result.
+  // If the result is 10, the check digit is 'X'. Otherwise, it's the digit itself.
+  const calculatedCheckDigit: string = result === 10 ? 'X' : String(result);
+
+  // Get the actual check digit from the input string.
+  const actualCheckDigit: string = baseStr.charAt(15).toUpperCase();
+
+  // Compare the calculated check digit with the actual one.
+  return calculatedCheckDigit === actualCheckDigit;
 }
diff --git a/tests/utils/assert.test.ts b/tests/utils/assert.test.ts
index e447958..e9143e4 100644
--- a/tests/utils/assert.test.ts
+++ b/tests/utils/assert.test.ts
@@ -4,11 +4,8 @@ import { isOrcidId } from '../../src/utils/assert';
 describe('isOrcidId', () => {
   test('should return true for valid ORCID IDs', () => {
     // Valid ORCID ID patterns
-    expect(isOrcidId('0000-0000-0000-0000')).toBe(true);
-    expect(isOrcidId('0000-0000-0000-000X')).toBe(true);
-    expect(isOrcidId('1234-5678-9012-3456')).toBe(true);
-    expect(isOrcidId('0000-0002-1825-009X')).toBe(true);
-    expect(isOrcidId('0000-0003-1527-0030')).toBe(true);
+    expect(isOrcidId('0009-0007-1106-8413')).toBe(true);
+    expect(isOrcidId('0000-0002-9079-593X')).toBe(true);
   });
 
   test('should return false for invalid ORCID IDs', () => {
@@ -31,5 +28,7 @@ describe('isOrcidId', () => {
     expect(isOrcidId('')).toBe(false); // Empty string
     expect(isOrcidId('abc-def-ghi-jkl')).toBe(false); // Letters instead of digits
     expect(isOrcidId('0000-0000-0000-000@')).toBe(false); // Invalid special character
+    expect(isOrcidId('0000-0001-5109-370X')).toBe(false); // Incorrect X position
+    expect(isOrcidId('0000-0002-1825-0098')).toBe(false); // Fails checksum
   });
 });