The RFC Validator checks whether a Mexican Registro Federal de Contribuyentes number has the correct check digit, applying the same modulo-11 algorithm used by SAT.
What it is
Every individual RFC has 13 characters: 4 letters (from the name), 6 digits of birth date, 2 homoclave characters, and 1 final check digit. That last character isn't arbitrary — it's computed from the 12 before it, and that's exactly the calculation this tool redoes.
Note: this tool validates only the mathematical structure of the number. It does not query SAT's database, so it can't confirm whether the RFC really exists, belongs to someone, or is active.
Who it's for
- Developers and QA testing registration flows for Mexican or Latin American customers.
- E-invoicing teams who need to validate the format before submitting to SAT.
- Anyone who wants a quick check that an RFC was typed without a digit error.
How the calculation works
The tool splits off the first 12 characters, converts each to its numeric value from SAT's table (digits keep their own value, letters run from 10 to 36, and there are special values for space, & and Ñ), multiplies each value by a descending weight from 13 to 2, and sums everything. The remainder of dividing by 11 defines the 13th character: remainder 0 gives digit 0, remainder 1 gives the letter A, and any other remainder gives 11 minus the remainder. If it matches what was typed, the RFC is valid.
How to use it
Paste the RFC into the field above and click Validate. The result appears instantly. If you need the reverse — creating valid RFCs to seed a test database — use the RFC Generator.