CUIT/CUIL Calculator (Argentina)

How is the CUIT/CUIL check digit calculated

Take the 10 digits (2-digit prefix + 8-digit DNI), multiply each by the weights 5,4,3,2,7,6,5,4,3,2 from left to right, add the products, and subtract the remainder of that sum divided by 11 from 11.

This tool only computes the mathematical check digit; it does not confirm the CUIT/CUIL actually exists or is active. Always verify against AFIP's official registry.

How is the CUIT/CUIL check digit calculated?

Form 10 digits from the 2-digit type prefix plus the 8-digit DNI, multiply each from left to right by the weights 5,4,3,2,7,6,5,4,3,2, add the products, and compute 11 minus the remainder of that sum divided by 11. Example: prefix 20 with DNI 12345678 gives check digit 6, i.e. 20-12345678-6.

Calculation steps

1. Choose the prefix by person type: 20 (male), 27 (female), 30 (legal entity), or 23 (other/non-binary, or the special case below).
2. Pad the DNI with a leading zero to 8 digits if it has only 7.
3. Multiply the 10 digits (prefix + DNI), left to right, by the weights 5,4,3,2,7,6,5,4,3,2.
4. Sum the 10 products and take the remainder of that sum divided by 11.
5. Subtract that remainder from 11: if the result is 11, the check digit is 0; if it is 10, the special prefix 23 with check digit 9 is used instead; otherwise it is the number itself.

Formula

• digit = each of the 10 digits (2-digit prefix + 8-digit DNI), read left to right
• weight = the multiplier for that position: 5,4,3,2,7,6,5,4,3,2
• mod 11 = the remainder of the total sum divided by 11

Quick CUIT answers

How is the CUIT check digit calculated for 20-12345678?

Multiply the 10 digits (prefix 20 + ID 12345678) by weights 5,4,3,2,7,6,5,4,3,2, sum them, take the remainder mod 11, and subtract from 11 (11 - remainder). For 20-12345678 that gives check digit 6, so the full CUIT is 20-12345678-6.

What does the 20 prefix mean?

20 marks a CUIT issued to a male individual (persona fisica).

What does the 27 prefix mean?

27 marks a CUIT issued to a female individual. For ID 12345678, that gives 27-12345678-0.

What does the 30 prefix mean?

30 marks a CUIT issued to a company or legal entity. For ID 12345678, that gives 30-12345678-1.

What does the 23 prefix mean?

23 is used for cases this tool groups as 'other' -- it's also the prefix the calculation itself falls back to whenever the raw check digit works out to 10 (see below).

What happens if the calculated check digit comes out to 10?

The tool switches the prefix to 23 and uses check digit 9 instead -- this special-case substitution is part of the standard CUIT algorithm, not an error.

What happens if the check digit comes out to 11?

It's set to 0.

If my ID number is only 7 digits, how is it handled?

The tool pads it with a leading zero to make 8 digits before calculating the check digit.

Example calculated CUIT/CUIL numbers

Frequently asked questions

What's the difference between CUIT and CUIL?

They're the same 11-digit number under different names depending on use: CUIL (Código Único de Identificación Laboral) is used for employment and social security contributions, while CUIT (Código Único de Identificación Tributaria) is used for AFIP tax registration. The check-digit algorithm is identical for both.

What does the special case mean when the check digit comes out to 10?

The modulo-11 algorithm only produces single digits 0-9. When the raw calculation equals exactly 10, AFIP's convention is to use prefix 23 (instead of 20, 23, or 27) together with check digit 9, rather than a two-digit value.

Does this calculator confirm the CUIT belongs to a real person?

No. It only verifies that the check digit is mathematically correct for the prefix-and-DNI combination you enter. It does not query any registry or confirm the number is active or registered — that requires AFIP's official registry.

Why are there multiple possible prefixes for the same person?

The prefix depends on taxpayer type (20 male, 27 female, 30 legal entity) and, in some historical or administrative cases, can vary (23, 24, 33, 34). AFIP is the only authoritative source for confirming which prefix applies to a real CUIT.

This tool implements only the public modulo-11 check-digit algorithm. It does not verify that a CUIT/CUIL actually exists, is active, or belongs to the stated person — use AFIP's official registry for real verification.

Privacy and safety

• Runs in your browser — Everything you type is calculated on your own device. Your inputs are never sent to a utilduck server.
• Encrypted connection — Pages are served over HTTPS, so nobody on the network can read what you load.
• Not shared with third parties — Your inputs are not passed to analytics or advertising services.
• Nothing is stored — Results are not saved to any server, and there is no account to create.

Last updated: 2026-08-17