Definition
You registered your business, then nothing happened for a few days. One morning an email lands with a nine-digit number and no instructions.
The following week your first client asks for "your SIRET", your bank wants an extrait Kbis (a company registration extract) you do not have, and a European form demands a VAT number.
Yet only one number was ever sent to you.
The SIREN is the identification number of your business: nine digits issued by INSEE, the national statistics institute, once the file you submitted at the One-stop shop reaches it.
It enters you in the répertoire Sirene, the register that lists every business established in France.
It identifies a business, not an activity: it says nothing about what you sell, nothing about what you collect, nothing about your tax regime.
One SIREN, several SIRET numbers
The most common mix-up sets these two numbers against each other, and a simple addition settles it.
The SIRET number is made of your SIREN, nine digits, followed by a five-digit NIC identifying the establishment: nine plus five, fourteen digits in all.
The SIREN identifies the business, the SIRET identifies the place where it operates. The first one never changes, the second changes as soon as the address does.
Camille, a graphic designer, registers in Lyon. INSEE issues her a SIREN and a first SIRET. She moves to Bordeaux, then to Nantes the following year, declaring each change of address.
After those two moves she holds one SIREN, the same one throughout, and three SIRET numbers, two of which point to closed establishments. Only the last one is active.
Her first nine digits have not shifted by a single digit across three addresses.
A third identifier appears on the same notice, the APE code, derived from the activity you described.
That one is primarily statistical: it decides neither your tax regime nor your contribution rates, which follow the real nature of your work.
A wrongly assigned code can be corrected with INSEE, but correcting it changes nothing in what you owe.
What your SIREN does not create
A shortcut circulates on forums: take your SIREN, add a country prefix and a check key in front of it, and consider yourself the holder of an EU VAT number.
This is where the page has to stop, because the mistake only surfaces when a European client rejects the invoice.
An intra-EU VAT number cannot be derived from a SIREN. That construction appears on no official page, and a number rebuilt by hand proves nothing until it has actually been issued.
The number is issued by the business tax office and then appears in your professional account.
Issuing it is free, and as long as you fall under the VAT exemption scheme it is in no way automatic: letters offering to obtain it for a fee are commercial offers, not a mandatory formality.
The same caution applies to the rest of your administrative situation.
The SIREN does not say whether you fall under the VAT exemption scheme, it does not say which contribution rate applies to you, and it is no proof that you are up to date with your payments.
It is only an identification key: everything else is read elsewhere, in your URSSAF account or in your professional space on the French tax administration website.
A public number, and what follows from it
The répertoire Sirene is published as open data.
Anyone can find a business by name on the Annuaire des entreprises (the official state business directory), and that is the first useful reflex before accepting a job from an unknown client.
It is also what explains the letter that arrives in the weeks after registration, with an official-looking logo, a file number and an amount to pay.
Registering a micro-enterprise is free, and no public body asks you by post to pay for an entry in a register: these Fraudulent register letters exploit data you never published yourself.
A sole trader can, incidentally, ask INSEE not to publish their details.
On the paperwork side, the question comes up whenever a bank account is opened: the bank asks for a Kbis, and many micro-entrepreneurs have none to hand over.
The document proving that you exist is a free download, the SIRENE status notice issued by INSEE, which carries your SIREN, your SIRET and your APE code; the Kbis extract does not concern everyone.
On an invoice, the legal requirement covers the identification number of the business, so the SIREN, while clients and supplier portals tend to ask for the SIRET, which is more precise.
Keep that one up to date after a move: a closed SIRET points to an establishment that no longer exists.
Frequently asked questions
Does my SIREN change if I move or add a new activity?
No. It is issued once and stays with you as long as the business exists, even if you change town, main activity or APE code.
It is the SIRET that changes with every new address, since its last five digits identify the establishment where you operate.
I lost the registration letter, where can I find my number again?
It appears on the Annuaire des entreprises, on the avis de situation SIRENE that INSEE makes available, and in your online URSSAF account.
None of those routes costs anything, and there is no application to file to recover a number that has already been issued.
Is my SIREN visible to everyone?
Yes.
The répertoire Sirene is public and released as open data: that is what lets a client check that you exist before trusting you with a job, and what lets marketing companies write to you.
A sole trader can ask INSEE not to publish their details.
Is a SIREN enough to invoice a client elsewhere in Europe?
No, and the answer depends on what you invoice.
A service sold to a business in another European Union country requires an intra-EU VAT number from the very first euro; other dealings with the European Union trigger it above a yearly amount, set out on the page devoted to that number.
It is requested from the business tax office, through the secure messaging of your professional account, and then appears in that account.
It is not built by adding letters in front of your SIREN, and obtaining it costs nothing at all.