From dff411ebf250808ceb0fc72253eb54358bb49c8b Mon Sep 17 00:00:00 2001
From: jassad095 <joaopfassad@gmail.com>
Date: Wed, 24 Jun 2026 14:30:11 -0300
Subject: [PATCH] fix: generate alphanumeric CNPJs using the full A-Z alphabet

---
 src/generate-cnpj/generate-cnpj.test.ts | 15 +++++++++++++++
 src/generate-cnpj/generate-cnpj.ts      |  2 +-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/generate-cnpj/generate-cnpj.test.ts b/src/generate-cnpj/generate-cnpj.test.ts
index caf865a1..8c9504f5 100644
--- a/src/generate-cnpj/generate-cnpj.test.ts
+++ b/src/generate-cnpj/generate-cnpj.test.ts
@@ -73,5 +73,20 @@ describe("generateCnpj", () => {
 				expect(isValidCnpj(formatted, { version: 2 })).toBe(true);
 			}
 		});
+
+		test("should generate alphanumeric CNPJs spanning the full A-Z alphabet", () => {
+			const usedChars = new Set<string>();
+			for (let i = 0; i < 1000; i++) {
+				for (const char of generateCnpj(2)) {
+					usedChars.add(char);
+				}
+			}
+			// E, O, T and U were previously excluded by a restricted alphabet, even
+			// though isValidCnpj accepts them: the RFB alphanumeric CNPJ uses the full
+			// [A-Z0-9] base (official example "12.ABC.345/01DE-35" contains an "E").
+			for (const char of ["E", "O", "T", "U"]) {
+				expect(usedChars.has(char)).toBe(true);
+			}
+		});
 	});
 });
diff --git a/src/generate-cnpj/generate-cnpj.ts b/src/generate-cnpj/generate-cnpj.ts
index 30ea86b4..589912b3 100644
--- a/src/generate-cnpj/generate-cnpj.ts
+++ b/src/generate-cnpj/generate-cnpj.ts
@@ -7,7 +7,7 @@ const FIRST_CHECK_DIGIT_WEIGHTS = [5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2];
 
 const SECOND_CHECK_DIGIT_WEIGHTS = [6, ...FIRST_CHECK_DIGIT_WEIGHTS];
 
-const VALID_CNPJ_CHARS = "0123456789ABCDFGHIJKLMNPQRSVWXYZ";
+const VALID_CNPJ_CHARS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
 
 const generateRandomCnpjChar = (): string =>
 	VALID_CNPJ_CHARS[Math.floor(Math.random() * VALID_CNPJ_CHARS.length)];