How is the CUIT/CUIL check digit calculated?

Multiply the first ten digits by the weights 5, 4, 3, 2, 7, 6, 5, 4, 3, 2 and sum them. The check digit is 11 minus (sum mod 11); a result of 11 becomes 0, and a result of 10 requires a special prefix reassignment.

What is the difference between CUIT and CUIL?

They share the same 11-digit structure and check-digit rule. CUIT is the tax identification key used by AFIP for taxpayers and companies, while CUIL is the labour identification key used for employees and SIPA pension records.

What do the first two digits mean?

The prefix marks the type: 20 and 27 are individual male and female, 23 and 24 are alternates used when the base DNI is shared, and 30, 33, 34 are companies and legal entities.

Does a valid check digit mean the number is registered?

No. A valid check digit only confirms the number is internally consistent. It does not confirm registration with AFIP; check the official constancia de inscripción for that.

Is my CUIT sent anywhere?

No. The check-digit calculation runs entirely in your browser, so the number never leaves your device.

Argentina CUIT/CUIL Validator

A CUIT (Clave Única de Identificación Tributaria) and CUIL (Clave Única de Identificación Laboral) are the 11-digit identity keys Argentina uses for tax and labour records. Both follow the same XX-DNI-Y structure: a two-digit type prefix, an eight-digit core (usually the DNI for individuals), and a final check digit. Before relying on a CUIT on an AFIP invoice or a CUIL on a SIPA pension filing, you can confirm it is well-formed with AFIP’s modulo-11 check. This free validator runs that exact check in your browser.

How it works

The eleventh digit is a check digit computed from the first ten:

Strip any dashes and spaces so you have 11 digits.
Multiply the first ten digits by the weights 5, 4, 3, 2, 7, 6, 5, 4, 3, 2.
Add the ten products to get the weighted sum.
Compute 11 - (sum mod 11). If the result is 11 the check digit is 0; if it is 10 the number requires a special prefix reassignment.
The number is valid when that value equals the eleventh digit.

The tool also decodes the two-digit prefix into its meaning (individual or company).

Example

For 20-12345678-?, apply the weights to 2 0 1 2 3 4 5 6 7 8. Suppose the weighted sum is 138; then 138 mod 11 = 6, so the check digit is 11 - 6 = 5. The full number 20-12345678-5 would therefore be valid, and any other final digit would fail.

A valid check digit confirms the number is well-formed, not that it is registered with AFIP. For invoicing or SIPA filings, confirm the status via the official constancia de inscripción. Everything here runs locally — your CUIT never leaves your device.