CUIT/CUIL Generator & Validator | Argentinian Tax ID Tool

Argentinian CUIT/CUIL Generator and Validator

A CUIT/CUIL is an 11-digit identification number used in Argentina for taxes and social security. This tool builds a number that passes the official check-digit formula, or checks whether a number someone has already given you passes it.

What is the difference between CUIT and CUIL?

CUIT stands for Clave Única de Identificación Tributaria ("Unique Tax Identification Key"). The tax authority AFIP (Administración Federal de Ingresos Públicos) assigns it to anyone who pays taxes, whether a person or a company.

CUIL stands for Clave Única de Identificación Laboral ("Unique Labor Identification Key"). It identifies a worker inside Argentina's social security and pension system.

The two numbers share the same 11-digit layout and the same check-digit formula. Many people end up with both: a CUIL from their first job, and later a CUIT if they register as self-employed or open a business.

CUIT/CUIL structure

A CUIT/CUIL is written as XX-XXXXXXXX-X, with three parts:

1. Type code (2 digits): identifies what kind of holder the number belongs to.
2. ID number (8 digits): for a person, this is their DNI (Documento Nacional de Identidad, Argentina's national ID number), padded with leading zeros if it has fewer than 8 digits. For a company, AFIP assigns this number directly.
3. Verification digit (1 digit): a check digit computed from the first 10 digits. It catches typos and made-up numbers.

Type codes

AFIP assigns codes 25 and 26 itself; a person or business never picks them, which is why the generator's dropdown does not list them, even though the validator still accepts them. Since 2021, Argentina no longer ties new CUIL prefixes to sex: a new individual can be assigned 20, 23, 24, or 27 without regard to gender, under Resolución 286/2021.

How to calculate the CUIT/CUIL verification digit

The verification digit comes from a weighted sum, then a division by 11.

1. Write the type code and the 8-digit ID number together, as 10 digits.
2. Multiply each digit by its weight, in this fixed order: 5, 4, 3, 2, 7, 6, 5, 4, 3, 2.
3. Add the 10 products together.
4. Divide the sum by 11 and keep the remainder.
5. Subtract the remainder from 11.

As a formula:

$VD = 11 - \left(\sum_{i=1}^{10} d_i \times w_i \bmod 11\right)$

Two results need special handling:

• If the result is 11, the verification digit is 0.
• If the result is 10, there is no valid verification digit for that type code and ID number. AFIP never issues that combination. It is not rounded down to 9 or to anything else. The number simply does not exist under that type code.

Worked example

Take type code 20 and DNI 12345678. The first 10 digits are 2, 0, 1, 2, 3, 4, 5, 6, 7, 8.

The products add up to 148. Dividing 148 by 11 gives a remainder of 5, since 11 × 13 = 143 and 148 − 143 = 5. Then 11 − 5 = 6.

The full number is 20-12345678-6.

What happens when no verification digit exists

Some type-code-and-ID combinations produce a remainder of 1, which would need a verification digit of 10. That is not a real digit. Take type code 20 and DNI 10000005: the weighted sum is 23, and 23 divided by 11 leaves a remainder of 1, so 11 − 1 = 10.

AFIP does not issue "20-10000005" at all. Instead it reissues the number under a related type code and recalculates the digit from there:

For DNI 10000005, the tool's generator produces 23-10000005-9 instead of anything starting with 20. The validator will reject 20-10000005-9, and every other last digit after 20-10000005, because no verification digit makes that type-code-and-DNI pairing valid.

Using the generator

Open the Generator tab and pick a type code. Type an 8-digit DNI, or leave the field blank for a random one. The tool shows a formatted, mathematically valid CUIT/CUIL immediately and lets you copy it with one click. If the type code chosen has no valid digit for that DNI, the tool automatically reissues the number under the related type code described above.

Using the validator

Open the Validator tab and type a CUIT/CUIL, with or without hyphens. Clicking Validate checks three things in order: that the input has exactly 11 digits, that the type code is one AFIP actually issues, and that the last digit matches the calculation. A valid result also shows the type code, ID number, and verification digit broken out separately.

Common mistakes

• Dropping the leading zero. DNI 1234567 must become 01234567 inside the CUIT/CUIL. Converting it to a plain integer for storage or comparison strips that zero and breaks the check-digit calculation.
• Treating every two-digit prefix as valid. Only 20, 23, 24, 25, 26, 27, 30, 33, and 34 exist. A number like 21-12345678-4 will always fail, no matter what the last digit is.
• Assuming a remainder of 1 rounds to a digit. It does not. That type-code-and-ID pairing has no valid CUIT/CUIL at all under the requested type code.
• Skipping AFIP's own records. A number can be mathematically correct and still not be registered with AFIP. Format checking alone cannot confirm a CUIT/CUIL belongs to a real, active taxpayer.

Frequently asked questions

What is the difference between CUIT and CUIL? CUIT identifies taxpayers; CUIL identifies workers in the social security system. Both use the same format and the same check-digit formula.

How is the CUIT/CUIL verification digit calculated? Multiply the first 10 digits by the weights 5, 4, 3, 2, 7, 6, 5, 4, 3, 2, add the products, divide by 11, and subtract the remainder from 11. A result of 11 becomes 0. A result of 10 means no valid number exists for that type code and ID.

Why did the generator give me a different type code than the one I chose? The type code and DNI you picked has no valid verification digit. AFIP reissues 20 as 23, 27 as 23, 30 as 33, and 34 as 33 in that situation, and the tool follows the same rule.

Which type codes belong to individuals, and which to companies? 20, 23, 24, 25, 26, and 27 belong to individuals. 30, 33, and 34 belong to companies and other organizations.

Can this tool generate a real, officially registered CUIT/CUIL? No. It generates numbers that pass the check-digit formula, the same way a tool can produce a credit card number that passes the Luhn algorithm without belonging to a real account. Registering a real CUIT or CUIL requires going through AFIP directly.

Are hyphens required when entering a CUIT/CUIL? No. Hyphens are only for display. The validator strips them automatically, so both "20-12345678-6" and "20123456786" work the same way.

References

1. AFIP (Administración Federal de Ingresos Públicos). "CUIT/CUIL/CDI." afip.gob.ar
2. "Clave Única de Identificación Tributaria." Wikipedia. es.wikipedia.org
3. Argentina.gob.ar. "CUIL - CUIT: nuevos números." argentina.gob.ar