France SIREN validator
How the SIREN format works
- Format
- 9-digit French business identifier (Luhn check digit)
- Example
- 552100554
Things to watch for
- 9 digits identifying a legal entity in France, checked with a standard Luhn (mod-10) algorithm
- Every French SIRET starts with its business's 9-digit SIREN, so the two identifiers share the same Luhn-valid prefix
- Checksum only — a Luhn-valid SIREN doesn't confirm the business is actually registered; check the official Sirene / annuaire-entreprises directory for that
^[0-9]{9}$A SIREN is the 9-digit number INSEE assigns to every legal entity registered in France — companies, associations, government bodies, even sole traders — the moment it’s entered into the Sirene directory. It’s a required reference on French invoices, contracts, and official filings, and it stays with the entity for its entire life, even if the business changes name, address, or activity.
Why the ninth digit exists
Like many national business-registration numbers, a SIREN carries a built-in Luhn check digit — the same mod-10 algorithm familiar from credit card numbers — computed across all nine digits. That single check digit is enough to catch a transposed or mistyped digit before it’s entered into accounting software, a supplier record, or an official filing, without needing to contact INSEE at all.
SIREN vs. SIRET
A SIREN identifies the legal entity as a whole, not any one of its physical locations. A business with a single head office and a business with fifty branches can hold the exact same 9-digit SIREN; what distinguishes each branch is a separate 14-digit SIRET, which is built by appending a 5-digit establishment code to that same SIREN.
What this check doesn’t tell you
Passing the Luhn check here confirms the number is internally consistent — nothing about whether INSEE actually issued it, or whether the business behind it is still active. INSEE’s Sirene directory, searchable through annuaire-entreprises.data.gouv.fr, is the authoritative source for confirming an actual, current registration.
Content last reviewed 2026-07-22.
SIREN FAQ
Who issues a SIREN and where is it recorded?
INSEE, France's national statistics institute, assigns a SIREN to every company, association, and public body when it registers, and lists it in the Sirene directory. It's the number that shows up on invoices, contracts, and official correspondence for that organization.
How is the SIREN's check digit calculated?
SIREN uses a standard Luhn (mod-10) algorithm, the same checksum family used to validate credit card numbers: digits are doubled from alternating positions, digits over 9 have 9 subtracted, and the total of all nine digits must be a multiple of ten. A single mistyped or transposed digit almost always breaks that total.
Does a Luhn-valid SIREN mean the business is currently registered?
No. A pass here confirms only that the 9 digits are arithmetically consistent — it doesn't check INSEE's Sirene directory, so it can't confirm the business exists, is still active, or was ever actually assigned that number. Use the official annuaire-entreprises.data.gouv.fr lookup to confirm registration.