Check a SIREN

Paste a SIREN: the tool validates its 9 digits with the Luhn formula and derives the intra-EU VAT number to expect (FR, key, SIREN). The number stays in your browser.

The calculation runs in your browser: the number you type is not sent to any server.

What this check proves

That the number is well-formed: the ninth digit is a Luhn check digit computed from the other eight. A typo or a made-up number fails.

What it does not prove

That the company exists or bears the name shown. The Annuaire des entreprises answers that for free; TrustyFile queries it automatically while analysing a document.

From SIREN to VAT number

In France the intra-EU VAT number derives from the SIREN: FR, a two-digit key, then the SIREN. The key is (12 + 3 × (SIREN mod 97)) mod 97. A VAT number whose key does not match the SIREN printed next to it is a strong warning sign — one of the inconsistencies TrustyFile looks for in an invoice.

The Luhn formula

• Double every other digit, starting with the second.
• If a doubled digit exceeds 9, subtract 9.
• Add up the 9 resulting digits.
• The total must be a multiple of 10.

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