Almost every foreign founder we work with mixes these two up at least once, usually on a form that gets rejected because the wrong number was used in the wrong field. Here is the actual difference, in plain terms.
SIREN identifies the company. SIRET identifies a location.
The SIREN is a 9-digit number that uniquely identifies your legal entity, the company itself, full stop. You will have exactly one SIREN for as long as that company exists.
The SIRET is 14 digits: your SIREN plus a 5-digit suffix (the NIC, numéro interne de classement) that identifies a specific physical establishment. A company with one office has one SIRET. A company that opens a second office, warehouse, or branch gets a second SIRET: same SIREN, different suffix.
In practice: if a form asks for your company's identity (tax filings, most B2B contracts, your K-bis), it usually wants the SIREN. If it asks specifically which location or establishment is invoicing or operating (some VAT and payroll contexts), it wants the SIRET.
You do not apply for either: they are issued automatically
There is no separate application. Both numbers are generated automatically the moment your company registration is processed through the Guichet Unique. You do not need to visit a separate office or file additional paperwork to receive them.
How long it actually takes
Timelines vary by structure: companies (SAS, SARL) typically receive their SIRET within a few days of the commercial court confirming registration, sometimes 48–72 hours if the file was complete and clean. Micro-entrepreneurs usually receive theirs within one to two weeks of declaring their activity. In both cases, you do not have to wait for the physical confirmation letter. Your number is searchable in the SIRENE public database (or via infogreffe.fr) as soon as it is issued.
Every business and self-employed individual in France needs both
This is not optional or structure-dependent. A SIREN and at least one SIRET are mandatory for every registered business and self-employed individual in France, from a solo micro-entrepreneur to a multinational subsidiary.
Where to look up a number for free
Both numbers are public. You can search any French business by name, SIREN or SIRET in the Annuaire des entreprises (annuaire-entreprises.data.gouv.fr), the State's company directory. Your own numbers also appear in your account on the Guichet unique once the registration is accepted.
Insee, the statistics office that keeps the Sirene register, has not issued a registration certificate since 1 January 2023. If someone asks you for written proof, you can download an "avis de situation" from avis-situation-sirene.insee.fr. It is free. It has no legal value and it is not a K-bis.
One warning: Insee's Sirene services cost nothing. A letter or e-mail asking you to pay for your Sirene registration is a scam.
What changes when you move, and what does not
The SIRET changes when the address of the company or of one of its establishments changes. Only the last five digits are new. The SIREN stays the same. You must report the move on the Guichet unique. A sole trader, including a micro-entrepreneur, keeps the same SIREN for life.
After a move, remember to update the SIRET on your payroll documents, your contracts and your supplier accounts.
Other numbers built on your SIREN
- VAT number. A French intra-community VAT number is the letters FR, a 2-digit key, then your 9-digit SIREN. The business tax office (SIE) sends it automatically to businesses that are liable for VAT. A business that is not liable has to ask for it through the messaging service of its professional account on impots.gouv.fr. You can check a partner's number on the European VIES service.
- APE code. Insee assigns this activity code (4 digits and 1 letter) automatically at registration. From 1 January 2027, every business gets a new APE code under the NAF 2025 classification. You can already see yours on sirene.gouv.fr.
- Invoices. Your SIREN is a mandatory mention on every invoice. Each missing or wrong mention can cost a fine of €15, capped at 25% of the invoice amount. Your business customer's SIREN is also becoming mandatory: from 1 September 2026 for large and mid-size companies, and from 1 September 2027 for small businesses and micro-entrepreneurs.
Where founders get stuck
The confusion rarely causes a real problem on its own. The common failure mode is a founder who invoices, opens a bank account, or files a form using the wrong number, then loses time correcting it. If you are opening your first business bank account or signing your first commercial lease, double-check which number the counterparty is actually asking for before you submit anything. See our guide on registering a company in France for the full sequence this fits into.