CUIT Validator

How it is calculated

All non-digits are stripped, so hyphens and spaces are fine, and exactly 11 digits must remain; otherwise the result is Invalid with a dash for both the check digit and the entity. The first ten digits are multiplied by the weights 5 4 3 2 7 6 5 4 3 2 and summed. The expected check digit is 11 − (sum mod 11), with 11 becoming 0. The CUIT is Valid when this equals the 11th digit.

If the formula gives 10 there is no single-digit check, so the tool always reports Invalid and shows a dash for the check digit. The two-digit prefix gives the entity type: 20, 23, 24 and 27 are reported as Persona (individual), 30, 33 and 34 as Empresa (company), and anything else as Unknown. Only the arithmetic and the prefix are checked; the tool cannot tell whether the number is actually registered with the tax authority.

Common mistakes

• Dropping a digit or typing only the 8-digit DNI. Anything other than 11 digits is Invalid, with dashes where the check digit and entity would be.
• Treating Valid as proof that the taxpayer exists. The check digit only catches typing errors; it says nothing about registration or whether the CUIT is active.
• Expecting the tool to tell men from women. It reports only Persona or Empresa; a prefix outside 20, 23, 24, 27, 30, 33, 34 shows Unknown, even if the check digit is correct.
• Entering another country's tax number. Any 11 digits get a checksum result, but a Valid or Invalid verdict only means something for Argentine CUITs.
• Reading the check digit shown for an Invalid number as the correction for your typo. It is only the digit expected for the first ten digits as entered, and if the typo is in those digits it will be wrong too.