Argentinian CBU Generator & Validator (BCRA Format)

A CBU (Clave Bancaria Uniforme) is a 22-digit code that identifies a bank account in Argentina. This tool generates random CBUs that pass the official check-digit rules, and checks whether an existing CBU is correctly formed.

What is a CBU?

Clave Bancaria Uniforme means "Uniform Bank Key" in Spanish. Argentina's central bank, the Banco Central de la República Argentina (BCRA), introduced the CBU in 2000 to give every bank account in the country a single, standard identifier. Before then, each bank used its own account-numbering system, which made electronic transfers between banks slow and error-prone.

Every active bank account in Argentina has exactly one CBU. Banks show it in their apps, on statements, and in online banking, and customers give it to anyone who needs to send them money by transfer.

CBU structure and format

A CBU is always 22 digits long, with no letters or spaces. It splits into two blocks:

• First block (8 digits): identifies the bank and branch. By convention, the first 3 digits are the bank code and the next 4 digits are the branch code. The 8th digit is a check digit.
• Second block (14 digits): identifies the account. The first 13 digits are the account number. The 14th digit is a check digit.

A check digit is a digit calculated from the other digits in a block. It lets a computer detect a mistyped or reordered digit without contacting a bank server. If a submitted CBU's check digit does not match what the formula produces, the CBU is rejected as invalid.

How to calculate the CBU check digit

Both check digits use the same method, called a weighted modulo-10 checksum. Each digit of the block's base number is multiplied by a fixed weight, the products are added together, and the final digit comes from that sum.

Steps:

1. Multiply each digit of the base number by its matching weight.
2. Add all the products together.
3. Divide the sum by 10 and keep the remainder.
4. If the remainder is 0, the check digit is 0. Otherwise, the check digit is 10 minus the remainder.

First block weights (applied to the first 7 digits): 7, 1, 3, 9, 7, 1, 3

Second block weights (applied to the first 13 digits of the second block): 3, 9, 7, 1, 3, 9, 7, 1, 3, 9, 7, 1, 3

Example: calculating a CBU

Start with a 7-digit base for the first block: 0110070.

The products add up to 11. The remainder after dividing by 10 is 1, so the check digit is 10 − 1 = 9. The first block is 01100709.

Now take a 13-digit base for the second block: 0003100056000. Multiplying each digit by its weight (3, 9, 7, 1, 3, 9, 7, 1, 3, 9, 7, 1, 3) and adding the products gives a sum of 75. The remainder after dividing by 10 is 5, so the check digit is 10 − 5 = 5. The second block is 00031000560005.

Joining both blocks gives the full CBU:

10110070900031000560005
2

This 22-digit code is a valid CBU, because both of its check digits match what the formula produces.

Using the generator

The generator tab fills the bank/branch and account positions with random digits, then computes both check digits with the formula above. The result is a 22-digit code that always passes validation, useful for filling test databases or checking how software handles CBU input, without using a real account number.

Using the validator

The validator tab checks a submitted CBU against four rules: it must be exactly 22 characters long, it must contain only digits, its 8th digit must match the check digit computed from the first 7 digits, and its 22nd digit must match the check digit computed from the 13 digits before it. If a rule fails, the tool reports which block is invalid.

Passing these checks confirms only that the CBU is correctly formed. It does not confirm that the account exists or is open, since that requires access to a bank's own records.

CBU and CVU

A CVU (Clave Virtual Uniforme) identifies an account at a digital wallet provider, such as a fintech payment app, rather than a traditional bank. A CVU uses the same 22-digit format and the same check-digit formula as a CBU, so the two are interchangeable for sending and receiving transfers.

Frequently asked questions

How many digits does a CBU have? Exactly 22. The first 8 identify the bank and branch, and the last 14 identify the account.

What is the difference between a CBU and a CVU? A CBU belongs to a bank account. A CVU belongs to a digital wallet account. Both use 22 digits and the same check-digit rules, and money can move between them like any other transfer.

Can a generated CBU be used for a real transfer? No. A generated CBU is only guaranteed to be correctly formed; it is not linked to any real account, so a transfer sent to it will fail or be rejected.

Why does a validator reject a CBU that looks correct? Usually because of a copy-paste error, such as an extra space, a missing digit, or two swapped digits. The check-digit formula is built to catch exactly these kinds of mistakes.

Does a valid CBU guarantee the account exists? No. The check digits only confirm the code follows the correct format. Confirming that an account is open and active requires checking with the bank itself.

Where can someone find their own CBU? In the account details section of their bank's mobile app or online banking, or on a printed account statement.