Check a French SIRET or SIREN number

A mistyped or made-up SIREN or SIRET shows up in a second thanks to its check digit. The tool below checks the number and gives the matching VAT number.

Updated October 14, 2026

SIREN vs SIRET

• The SIREN (9 digits) identifies the company. It's unique and never changes.
• The SIRET (14 digits) identifies an establishment: the SIREN followed by a 5-digit number, the NIC. A company has one SIRET per establishment (head office, shops, branches…).

The seller's SIREN or SIRET is mandatory on French invoices; with the e-invoicing reform, the customer's SIREN is too.

How the check digit works

The last digit of a SIREN and of a SIRET is computed with the Luhn algorithm: double every second digit from the right (subtracting 9 when the result exceeds 9), add everything up, and the total must be a multiple of 10.

One known exception: La Poste's establishments (SIREN 356 000 000), whose SIRET is checked with the plain sum of digits, a multiple of 5.

A valid check digit doesn't prove the company exists: a made-up number is right by chance one time in ten.

Does the company exist?

The French government's free company directory gives, for a SIREN or SIRET: name, address, activity, creation date and, above all, whether the company or establishment is active or closed. An invoice from a closed company is a strong warning sign.

The VAT number follows from the SIREN

A French VAT number is FR + a 2-digit key + the SIREN. The tool above computes it; to check an existing VAT number, use the VAT number tool.