diff --git a/src/__tests__/usevalidationsbr.spec.ts b/src/__tests__/usevalidationsbr.spec.ts
index c16d551..d3057d4 100644
--- a/src/__tests__/usevalidationsbr.spec.ts
+++ b/src/__tests__/usevalidationsbr.spec.ts
@@ -13,14 +13,18 @@ describe('UseValidationBr Cep', () => {
 
 describe('UseValidationBr CNPJ', () => {
   it('should be able return true to valid CNPJ', () => {
+    expect.assertions(2);
+
     expect(useValidationsBR('cnpj', '66.919.381/0001-15')).toBe(true);
+    expect(useValidationsBR('cnpj', '12.ABC.345/01DE-35')).toBe(true);
   });
 
   it('should be able return false to invalid CNPJ', () => {
-    expect.assertions(2);
+    expect.assertions(3);
 
     expect(useValidationsBR('cnpj', '12.732.455/0001-25')).toBe(false);
     expect(useValidationsBR('cnpj', '66.919.381/0001-10')).toBe(false);
+    expect(useValidationsBR('cnpj', '12.ABC.345/01DE-34')).toBe(false);
   });
 
   it('should be able return false to pass a empty string', () => {
@@ -28,7 +32,10 @@ describe('UseValidationBr CNPJ', () => {
   });
 
   it('should be able return false to pass a string over 14 characters', () => {
+    expect.assertions(2);
+
     expect(useValidationsBR('cnpj', '66.919.381/00001-14')).toBe(false);
+    expect(useValidationsBR('cnpj', '12.ABC.345/001DE-35')).toBe(false);
   });
 
   it('should be able return false to pass a only repeated numbers', () => {
diff --git a/src/__tests__/validateCNPJ.spec.ts b/src/__tests__/validateCNPJ.spec.ts
index a6ba706..1097ceb 100644
--- a/src/__tests__/validateCNPJ.spec.ts
+++ b/src/__tests__/validateCNPJ.spec.ts
@@ -4,6 +4,8 @@ import { validateCNPJ } from '../validations/validateCNPJ';
 describe('validateCNPJ', () => {
   it('should return true for valid CNPJs', () => {
     expect(validateCNPJ('66.919.381/0001-15')).toBe(true);
+    expect(validateCNPJ('12.ABC.345/01DE-35')).toBe(true);
+    expect(validateCNPJ('12ABC34501DE35')).toBe(true);
   });
 
   it('should return false for invalid CNPJs', () => {
@@ -12,15 +14,22 @@ describe('validateCNPJ', () => {
     expect(validateCNPJ('12.732.455/0001-25')).toBe(false);
     expect(validateCNPJ('66.919.381/0001-10')).toBe(false);
     expect(validateCNPJ('123')).toBe(false);
+    expect(validateCNPJ('12.ABC.345/01DE-34')).toBe(false);
+    expect(validateCNPJ('VQ.A8K.XRA/0001-49')).toBe(false);
+    expect(validateCNPJ('12abc34501de35')).toBe(false);
+    expect(validateCNPJ('49YYDYRJ000168')).toBe(false);
+    expect(validateCNPJ('12ABC34501DEAB')).toBe(false);
   });
 
   it('should return false for empty or null strings', () => {
     expect(validateCNPJ('')).toBe(false);
   });
 
-  it('should return false for CNPJs with all digits the same', () => {
+  it('should return false for CNPJs with all characters the same', () => {
     expect(validateCNPJ('11.111.111/1111-11')).toBe(false);
     expect(validateCNPJ('22222222222222')).toBe(false);
+    expect(validateCNPJ('BB.BBB.BBB/BBBB-BB')).toBe(false);
+    expect(validateCNPJ('AAAAAAAAAAAAAA')).toBe(false);
   });
 
   it('should return false for CNPJs with incorrect length', () => {
@@ -28,5 +37,9 @@ describe('validateCNPJ', () => {
     expect(validateCNPJ('66.919.381/0001-155')).toBe(false);
     expect(validateCNPJ('6691938100011')).toBe(false);
     expect(validateCNPJ('669193810001155')).toBe(false);
+    expect(validateCNPJ('12.ABC.345/01DE-3')).toBe(false);
+    expect(validateCNPJ('12.ABC.345/01DE-355')).toBe(false);
+    expect(validateCNPJ('12ABC34501DE3')).toBe(false);
+    expect(validateCNPJ('12ABC34501DE355')).toBe(false);
   });
 });
diff --git a/src/validations/validateCNPJ.ts b/src/validations/validateCNPJ.ts
index ac23ee8..a16a160 100644
--- a/src/validations/validateCNPJ.ts
+++ b/src/validations/validateCNPJ.ts
@@ -1,40 +1,55 @@
 import { isRepeated } from './utils';
 
 /**
- * The function `validateCNPJ` validates a Brazilian CNPJ number.
+ * The function `charToNumber` converts a CNPJ character into the number used by the
+ * check digit calculation. Following the Receita Federal spec, the ASCII value of the
+ * character is offset by 48, so digits map to themselves ('0' -> 0) and uppercase
+ * letters to their code ('A' -> 17).
+ * @param {string} char - A single character from the CNPJ base.
+ * @returns The numeric value used in the weighted checksum.
+ */
+function charToNumber(char: string): number {
+  return char.charCodeAt(0) - 48;
+}
+
+/**
+ * The function `generateChecksum` calculates a checksum based on a given base and a weight
+ * array. Each character in the `base` is converted with `charToNumber` and multiplied by the
+ * corresponding weight at the same index.
+ * @param {string} base - The value for which the checksum is calculated.
+ * @param {number[]} weight - The weights applied to each character of the base.
+ * @returns The calculated MOD 11 check digit.
+ */
+function generateChecksum(base: string, weight: number[]): number {
+  const sum = base
+    .split('')
+    .reduce((acc, char, i) => acc + charToNumber(char) * weight[i], 0);
+  const remainder = sum % 11;
+
+  return remainder < 2 ? 0 : 11 - remainder;
+}
+
+const weights1 = [5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2];
+const weights2 = [6, 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2];
+
+/**
+ * The function `validateCNPJ` validates a Brazilian CNPJ number, supporting both the
+ * traditional numeric format and the alphanumeric format (12 uppercase alphanumeric
+ * positions followed by 2 numeric check digits).
  * @param {string} value - The `value` parameter is a string that represents the CNPJ (Cadastro
- * Nacional da Pessoa Jurídica) number to be validated. It can be formatted with or without punctuation,
- * like '00.000.000/0000-00' or '00000000000000'.
+ * Nacional da Pessoa Jurídica) number to be validated. It can be formatted with or without
+ * punctuation, like '00.000.000/0000-00', '00000000000000' or '12.ABC.345/01DE-35'.
  * @returns The function `validateCNPJ` returns a boolean value. It returns `true` if the CNPJ is
  * valid, and `false` otherwise.
  */
 export function validateCNPJ(value: string): boolean {
-  const cnpj = String(value).replace(/[^\d]+/g, '');
-
-  if (cnpj === '' || cnpj.length !== 14 || isRepeated(cnpj)) {
-    return false;
-  }
-
-  const calculateDigit = (numbers: string, weights: number[]): number => {
-    let sum = 0;
-    for (let i = 0; i < numbers.length; i++) {
-      sum += parseInt(numbers.charAt(i), 10) * weights[i];
-    }
-    const remainder = sum % 11;
-    return remainder < 2 ? 0 : 11 - remainder;
-  };
-
-  const weights1 = [5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2];
-  const first12 = cnpj.substring(0, 12);
-  const dv1 = calculateDigit(first12, weights1);
-
-  if (dv1 !== parseInt(cnpj.charAt(12), 10)) {
-    return false;
-  }
-
-  const weights2 = [6, 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2];
-  const first13 = cnpj.substring(0, 13);
-  const dv2 = calculateDigit(first13, weights2);
-
-  return dv2 === parseInt(cnpj.charAt(13), 10);
+  const cnpj = String(value).replace(/[./-]/g, '');
+
+  if (!/^[A-Z\d]{12}\d{2}$/.test(cnpj) || isRepeated(cnpj)) return false;
+
+  const base = cnpj.substring(0, 12);
+  const dv1 = generateChecksum(base, weights1);
+  const dv2 = generateChecksum(base + dv1, weights2);
+
+  return `${dv1}${dv2}` === cnpj.substring(12);
 }