Clave Única de Identificación Tributaria / Laboral
Argentina · Individuals and companies
Paste or type the number — punctuation is optional.
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What this check does — and what it cannot do
This tool checks the number's structure and its check digit, using the published algorithm for that document. A number that passes is well formed: it is arithmetically consistent and could have been issued.
It cannot tell you whether the number was actually issued, whether it is active, or who it belongs to. Only the issuing tax authority can confirm that, through its own lookup service. Treat a passing result as "worth submitting", never as proof of identity.
The generator produces numbers that satisfy the same checksum, for filling forms while developing and testing software. They are arithmetic, not records: they are not drawn from any register and do not correspond to a real holder. No generator is offered for the US Social Security Number.
A CUIT contains the person's national ID number in plain sight
Unlike identifiers that are issued independently, the Argentine CUIT is assembled from an existing one. The middle eight digits are the holder's DNI, and the two-digit prefix marks what kind of taxpayer it is. Anyone who sees a CUIT therefore already has the DNI — which is worth knowing before you print one on an invoice.
How it works
- Recomputes the final check digit with the fixed weight sequence 5 4 3 2 7 6 5 4 3 2 and compares it to the one given.
- Reads the prefix, which distinguishes individuals from companies and other legal entities.
- Confirms the DNI embedded in the middle, since the two identifiers are not independent.
format PP-DDDDDDDD-C PP prefix: 20 / 23 / 24 / 27 individuals, 30 / 33 / 34 legal entities DD… the holder's DNI, unchanged C check digit check = 11 − (Σ digit × weight) mod 11, weights 5 4 3 2 7 6 5 4 3 2 11 → 0, 10 → 9
Worked example
Building a CUIT around DNI 12345678.
- prefix 20 gives 20-12345678, weighted sum reduces mod 11
- check digit works out to 6 → 20-12345678-6
- prefix 27 over the same DNI gives check digit 0 → 27-12345678-0
- the DNI is identical in both; only the prefix and check digit move
The same eight digits sit inside every CUIT built for that person. Changing the prefix changes the check digit but never hides the DNI.
Reading the result
- This is a genuine privacy property rather than a quirk. A CUIT on a public invoice discloses the holder's DNI to everyone who reads it, and the prefix conventionally reflects registered sex for individuals. Treat a CUIT with the same care as the DNI itself.
- The 23, 24, 25 and 26 prefixes exist because the check-digit calculation sometimes overflows for a given DNI under 20 or 27. They are a mechanical fallback, not a different category of person.
- Prefixes 30, 33 and 34 belong to companies and other legal entities, which have no DNI. For those, the middle digits are allocated by AFIP rather than derived from anything.
- As with every checksum, a valid CUIT means the digits are internally consistent. Whether it was issued, and to whom, only AFIP can confirm.
Common questions
- Can I derive someone's CUIT from their DNI?
- Usually yes for individuals — the prefix is conventional and the check digit is computed. That is precisely why a CUIT should not be treated as a secret or used as any kind of authentication factor.
- Why are there several prefixes for individuals?
- 20 and 27 are the conventional defaults; 23, 24, 25 and 26 are used when the check-digit arithmetic overflows for that DNI. The alternative prefix is chosen so that a valid check digit exists, nothing more.