SIRET / SIREN Number Validator
Instantly check whether a SIRET (14 digits) or SIREN (9 digits) number is valid using the Luhn control-key check. Automatic format detection, La Poste exception handled, runs 100% in your browser.
Check a number
How does SIRET validation work?
A SIRET (14 digits) or SIREN (9 digits) number embeds a control key computed with the Luhn algorithm, the same one used for credit-card numbers. This algorithm does not prove a company exists: it simply guarantees the number is mathematically consistent and catches most typos.
The principle: starting from the rightmost digit, double every second digit (subtracting 9 if the result exceeds 9), then sum everything. If the total is a multiple of 10, the key is correct.
Example: SIREN 732 829 320
| Digit (left to right) | 7 | 3 | 2 | 8 | 2 | 9 | 3 | 2 | 0 |
|---|---|---|---|---|---|---|---|---|---|
| Every second digit doubled | 7 | 6 | 2 | 16→7 | 2 | 18→9 | 3 | 4 | 0 |
7 + 6 + 2 + 7 + 2 + 9 + 3 + 4 + 0 = 40 → 40 mod 10 = 0 ✓
The La Poste exception
La Poste establishments (SIREN 356 000 000) do not follow the Luhn algorithm for historical reasons. For these numbers the rule is different: the sum of the 14 digits must be a multiple of 5. Many validators miss this case — ours handles it automatically.
Valid format ≠ real company
This validator checks the consistency of the number, not whether the company exists. A number can pass the Luhn check without matching any registered company. To verify that a company really exists and learn its status, use the official sources:
- annuaire-entreprises.data.gouv.fr — the official, free government directory
- INSEE's Sirene database
For the detailed steps, read our guide: how to verify a SIRET.
SIREN, SIRET, NIC: format reminder
| Identifier | Format | Role |
|---|---|---|
| SIREN | 9 digits | Identifies the business (legal entity) |
| SIRET | 14 digits (SIREN + NIC) | Identifies a specific establishment |
| NIC | 5 digits | Internal Classification Number (the last 5 digits of the SIRET) |
FAQ
A valid SIRET number has 14 digits and satisfies the Luhn algorithm: doubling every second digit (from the right) and summing all digits must give a multiple of 10. The SIREN (first 9 digits) follows the same rule. Our validator runs this check instantly, without sending your data to any server.
This validator only checks the mathematical consistency of the number (its format and control key). A number can be format-valid yet match no real company. To confirm a company's existence and status, use the official business directory (annuaire-entreprises.data.gouv.fr) or INSEE's Sirene database.
La Poste establishments (SIREN 356 000 000) are a historical exception: their SIRET numbers do not follow the Luhn algorithm. For them, the rule is that the sum of the 14 digits must be a multiple of 5. Our validator applies this exception automatically.
The control key is not a separate digit: it is embedded in the number through the Luhn algorithm. This mechanism detects common entry errors (a wrong digit, two transposed digits) before you even query a database.
Yes. Enter 9 digits and the tool validates the SIREN; enter 14 digits and it validates the SIRET. Format detection is automatic and spaces are ignored.
No. Validation runs entirely in your browser, in JavaScript. No number you enter is sent to our servers or stored.
Need valid SIRET numbers for your tests?
Our generator creates SIRET/SIREN numbers that pass the Luhn check, with realistic French companies and addresses.