France SIREN / SIRET Validator
Check a French SIREN (9-digit company) or SIRET (14-digit establishment) number with the Luhn checksum. 100% local. Built for France.
Batch check — paste many, one per line
Validate a French SIREN or SIRET
Enter a 9-digit SIREN or 14-digit SIRET to verify its Luhn checksum. Spaces are ignored. Everything runs locally in your browser.
How SIREN and SIRET numbers work
Every French business is identified by INSEE, the national statistics institute, in the Sirene register. The identifier has two layers, and each layer ends with its own check digit computed with the Luhn formula, the same test used on payment card numbers.
Structure
| Part | Length | What it identifies |
|---|---|---|
| SIREN | 9 digits | The legal unit: a company, an association or a sole trader. It is assigned once and kept for the life of the business; the 9th digit is the check digit. The RCS number quoted on legal documents is this same number. |
| NIC | 5 digits | The establishment: one physical location of the legal unit. Four sequence digits plus a check digit. It changes when the establishment moves. |
| SIRET | 14 digits | SIREN followed by NIC. Invoices and quotes issued in France must show the SIRET of the issuing establishment. |
Numbers are usually printed in groups of three (and five for the NIC), for example 732 829 320 00074. The grouping is cosmetic; the checker ignores spaces, dots and hyphens.
Worked example: the Luhn check on SIREN 732 829 320
Starting from the rightmost digit, every second digit is doubled. When doubling gives a two-digit result, 9 is subtracted (16 becomes 7). All the resulting digits are added up, and the number passes when the total is a multiple of 10.
| Digit | 7 | 3 | 2 | 8 | 2 | 9 | 3 | 2 | 0 | Sum |
|---|---|---|---|---|---|---|---|---|---|---|
| Doubled | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | |
| Result | 7 | 6 | 2 | 16 | 2 | 18 | 3 | 4 | 0 | |
| Kept | 7 | 6 | 2 | 7 | 2 | 9 | 3 | 4 | 0 | 40 |
The total is 40, a multiple of 10, so the SIREN passes. For the 14-digit SIRET 732 829 320 00074 the same test runs twice: the first 9 digits must pass on their own, and all 14 digits must pass together (their Luhn total is 50). Checking the two layers separately is what lets the tool report which part of a SIRET is wrong.
The La Poste exception
Every La Poste establishment shares the SIREN 356 000 000. With thousands of post offices, five-digit NICs that also satisfy Luhn ran out, so INSEE authorised a fallback rule for this one SIREN: a SIRET is accepted when the plain sum of its 14 digits is a multiple of 5.
INSEE's guidance is to run the normal Luhn test first and use the digit-sum rule only when Luhn fails. The head office SIRET 356 000 000 00048 passes Luhn (its digit sum is 26, which is not a multiple of 5), while the Rennes office 356 000 000 09075 fails Luhn but has a digit sum of 35. This tool applies both rules in that order; naive validators reject thousands of real post offices.
From SIREN to the French VAT number
The intra-EU VAT number of a French company is FR, a two-digit key and the SIREN. The key is computed as (12 + 3 × (SIREN mod 97)) mod 97. For SIREN 732 829 320 the key is 44, giving FR44732829320. The tool derives it for every valid SIREN; whether the company is actually registered for VAT can be confirmed in the European Commission's VIES service.
Official sources
- INSEE: official definition of SIREN, NIC and SIRET and of the Luhn check digit
- Annuaire des Entreprises: the French government's free public register to look up any SIREN or SIRET
- VIES: European Commission service to confirm that a VAT number is registered
Common mistakes and what a checksum cannot tell you
- A passing checksum means the digits are self-consistent. It does not mean the company exists, is still active or is the one you are dealing with; confirm identity in the official register.
- SIREN and SIRET are often mixed up: a 9-digit number is the company, a 14-digit number is one establishment of that company.
- A SIREN can start with 0. Dropping the leading zero leaves 8 digits, which the tool reports as a wrong length.
- The Luhn formula catches every single-digit typo and almost every swap of two neighbouring digits, but it cannot detect 09 swapped with 90.
- Validators that ignore the La Poste rule wrongly reject real post-office SIRETs; validators that apply only the digit-sum rule wrongly reject the La Poste head office.
In France, SIREN (9 digits) identifies a legal entity and SIRET (14 digits = SIREN + 5-digit NIC) identifies each establishment; both are assigned by INSEE. Standard validation is the Luhn algorithm: doubling every second digit from the right and requiring the total to be a multiple of 10. This tool applies Luhn to SIREN and SIRET, splits a SIRET into its SIREN and NIC parts, and explains failures — all locally in your browser.
Known edge case: establishments of La Poste (SIREN 356 000 000) are the official exception documented by INSEE. Their SIRETs are first tested with Luhn like any other; when Luhn fails, the SIRET is still accepted if the plain sum of its 14 digits is a multiple of 5. This tool applies both rules in that order, so the La Poste head office (which passes Luhn) and its thousands of post offices (which pass the digit-sum rule) are both recognised.
FAQ
What is the difference between SIREN, SIRET and NIC?
SIREN (9 digits) = the company or legal unit. NIC (5 digits) = one specific establishment of that company. SIRET = SIREN + NIC (14 digits). A company that moves offices keeps its SIREN but gets a new NIC, so its SIRET changes.
How does the Luhn check work here?
From the rightmost digit, double every second digit; if doubling gives more than 9, subtract 9. Add everything up: a valid SIREN or SIRET totals a multiple of 10. For SIREN 732 829 320 the total is 40. A SIRET is tested twice, once on its 9-digit SIREN and once on all 14 digits.
Why does a La Poste SIRET fail the normal check?
La Poste (SIREN 356 000 000) is the exception documented by INSEE: when one of its SIRETs fails Luhn, it is still valid if the sum of all 14 digits is a multiple of 5. The head office SIRET passes ordinary Luhn; most post offices pass only the digit-sum rule. This tool applies both rules in that order.
Can I get the VAT number from a SIREN?
Yes. The French intra-EU VAT number is FR + a two-digit key + the SIREN, with the key computed as (12 + 3 × (SIREN mod 97)) mod 97. For 732 829 320 the key is 44, giving FR44732829320. Whether the company is actually VAT-registered can be confirmed in the European Commission VIES service.
Does a valid result mean the company exists?
No. A passing checksum only shows the digits are self-consistent. To confirm a business is registered and still active, look it up in Annuaire des Entreprises (annuaire-entreprises.data.gouv.fr), the free official register built on INSEE Sirene data.
Where do I find a SIREN or SIRET?
On the Kbis extract, on invoices and quotes (French law requires the SIRET on invoices), in the legal footer of most company websites, and in the public Sirene register. The RCS number quoted on legal documents is the SIREN.
Is my number uploaded when I check it?
No. Validation runs entirely in your browser, including batch checks and CSV export.
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