Système d'identification du répertoire des entreprises / des établissements
France · Companies
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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.
Calculated in your browser. Nothing you enter is sent anywhere.
The French VAT number is not stored anywhere — it is calculated from the SIREN
A company's VAT number looks like an extra identifier it was issued. It is not: the two digits after FR are derived arithmetically from the nine-digit SIREN, as (12 + 3 × SIREN mod 97) mod 97. La Poste's real SIREN 356000000 gives key 39, so its VAT number is FR39356000000 — and you can work that out for any French company without asking.
How it works
- Runs the Luhn check over a 9-digit SIREN or a 14-digit SIRET.
- Derives the French VAT number from the SIREN.
- For a SIRET, separates the establishment number and flags the head office.
SIREN: 9 digits, Luhn · SIRET: SIREN + 5-digit NIC, Luhn over all 14 VAT key = (12 + 3 × (SIREN mod 97)) mod 97 VAT number = FR + key + SIREN the head office historically carries NIC 00001
Worked example
La Poste's published SIREN.
- 356000000 passes the Luhn check
- 356000000 mod 97 = 61
- (12 + 3 × 61) mod 97 = 195 mod 97 = 39
- the VAT number is therefore FR39356000000
- a SIRET adds five digits identifying one establishment of that company
One number that generates another. Knowing the rule means a missing VAT number is never a reason to delay an invoice — though it is still worth confirming the company is actually VAT-registered.
Reading the result
- SIREN identifies the company, SIRET identifies one of its sites. A firm has exactly one SIREN and as many SIRETs as it has establishments, so quoting a SIRET tells you which office or shop, not just which business.
- Luhn has a known blind spot: it cannot detect a 0 and a 9 swapping places. Since SIREN uses Luhn, a transposed 09 in a company number will still validate. Read the digits carefully off documents.
- The check confirms arithmetic, not existence or trading status. A company may be struck off, dormant, or not VAT-registered at all while its number still passes; the official register is the authority for anything that matters.
- A generator is offered because these identify businesses rather than people, and populating a test system with well-formed company numbers is ordinary work.
Common questions
- What is the difference between SIREN and SIRET?
- The SIREN is the 9-digit number of the company itself and stays the same for its whole life. The SIRET is 14 digits: the SIREN plus a 5-digit NIC identifying one establishment, so a company has one SIRET per site, and a site that moves gets a new one. You can enter either here; for a SIRET the tool checks all 14 digits and shows the establishment number.
- How do I get a French company’s VAT number from its SIREN?
- Compute the key as (12 + 3 × (SIREN mod 97)) mod 97, then write FR, the two-digit key and the SIREN. This tool does that for you once a SIREN or SIRET passes. Because the number is derived, confirm that the company is actually VAT-registered, for example through the EU’s VIES service, before relying on it.
- How can I check that a SIREN or SIRET belongs to a real, active company?
- Look it up in INSEE’s Sirene register, which anyone can search, for example through the government’s Annuaire des Entreprises. It shows the company name, address and whether the company or establishment is active or closed. This tool only runs the Luhn check, which the number of a closed company still passes.