What is a CUIL in Argentina?

CUIL stands for Código Único de Identificación Laboral — Unique Labour Identification Code. It is issued by ANSES (the national social security administration) and is used for employment, payroll, and social-security purposes. It is closely related to the CUIT (tax ID) and uses the same 11-digit format and check-digit algorithm, but CUIL is specifically the labour/employment identifier for individuals.

How is the CUIL check digit calculated?

Multiply the first 10 digits by the weights [5, 4, 3, 2, 7, 6, 5, 4, 3, 2], sum the products, take sum mod 11, then compute 11 minus that remainder. If the result is 11 the check digit is 0; if it is 10 the check digit is 9 (and the prefix is typically 23 or 24). Otherwise the check digit equals the result.

What do the two-digit CUIL prefixes mean?

The first two digits indicate the individual's gender category as recorded by ANSES: 20 = male (hombre), 27 = female (mujer), 23 or 24 = ambiguous (used when the standard 20 or 27 prefix would produce an invalid check digit for that particular DNI). All four are valid for individuals.

What is the difference between CUIL and CUIT?

CUIL (Código Único de Identificación Laboral) is the social-security/employment ID issued by ANSES for individuals. CUIT (Código Único de Identificación Tributaria) is the tax ID issued by AFIP and extends to companies (prefixes 30, 33, 34). Both use the identical 11-digit format and the same mod-11 check-digit algorithm, so a CUIL and CUIT for the same person are usually identical.

Does a valid checksum mean the CUIL is active?

No. A valid checksum only confirms that the 11 digits are internally self-consistent under the mod-11 rule. It does not verify that the CUIL was ever issued or that it belongs to a real person currently registered with ANSES. For official verification contact ANSES directly.

Is my CUIL sent to any server?

Never. All arithmetic runs inside your browser using JavaScript. No number, name, or any other data leaves your device. The page has no analytics that capture form input.

Argentina CUIL Validator

The CUIL (Código Único de Identificación Laboral — Unique Labour Identification Code) is the 11-digit identifier that Argentina’s ANSES assigns to every individual for employment and social-security purposes. Employers use it on payslips, contracts, and government filings; employees see it on their recibo de sueldo (pay stub). Before you submit a payroll record, integrate an HR system, or build an Argentine tax-compliance workflow, you need to know whether the CUIL your user provided is internally consistent. This validator runs the official ANSES mod-11 check-digit algorithm entirely in your browser — private, instant, and free.

How it works

A CUIL is always 11 digits in the form PP-DDDDDDDD-V:

PP — 2-digit type prefix: 20 (male), 27 (female), 23/24 (ambiguous, used when the standard prefix would produce an impossible check digit for a particular DNI).
DDDDDDDD — the person’s 8-digit DNI (Documento Nacional de Identidad).
V — a single check digit computed from the other 10 digits.

Check-digit algorithm

ANSES and AFIP both use the following mod-11 rule (identical for CUIL and CUIT):

Take the first 10 digits.
Multiply each by the fixed weight at its position: [5, 4, 3, 2, 7, 6, 5, 4, 3, 2]
Sum all 10 products.
Compute remainder = sum mod 11.
Compute candidate = 11 − remainder.
Apply the edge cases:
- If candidate = 11 → check digit is 0.
- If candidate = 10 → check digit is 9 (prefix is 23 or 24 in this situation).
- Otherwise → check digit equals candidate.

The validator shows you the weighted sum, the raw remainder, and the final candidate so you can verify every arithmetic step.

Worked example

Take the obviously-fake CUIL 20-12345678-6 (no real person intended):

Position	Digit	Weight	Product
1	2	5	10
2	0	4	0
3	1	3	3
4	2	2	4
5	3	7	21
6	4	6	24
7	5	5	25
8	6	4	24
9	7	3	21
10	8	2	16
Sum			148

148 mod 11 = 5 → 11 − 5 = 6 → check digit = 6. The full valid CUIL is 20-12345678-6.

Field	Value
Prefix	20 — Male (Hombre)
DNI segment	12345678
Check digit	6 (correct)
Weighted sum	148
148 mod 11	5 → 11 − 5 = 6

Formula note

The mod-11 family of check-digit algorithms is widespread in national ID systems because a single transposed digit almost always produces a different remainder — catching the most common data-entry errors. The ANSES/AFIP variant uses the ascending–descending weight pattern [5,4,3,2,7,6,5,4,3,2], which cycles through two decreasing runs. The two special cases (candidate 11→0, candidate 10→9) exist because a single decimal digit can only hold values 0–9; the prefix 23/24 is the administrative solution when 20 or 27 would demand an impossible check digit.