Definition
The first real client shows up, the job is agreed, and their accounts department asks for one thing before creating your supplier record: your SIRET number.
You declared your activity twelve days ago, no letter has arrived, and nobody explained whether this number is applied for, bought, or simply received.
The SIRET is the identifier of your establishment in the répertoire SIRENE (the national business register kept by INSEE, the French statistics institute).
It reads in two parts: your SIREN number, nine digits identifying the company, then a NIC of five digits identifying the place where it operates.
Fourteen digits in all, issued with no extra paperwork once you have declared your activity at the One-stop shop, together with your code APE (the activity code).
The SIREN identifies the company, the SIRET identifies one establishment, meaning one trading address.
Most micro-entrepreneurs have a single one, mix the two up with no harm done, and discover the difference on the day one of them changes and the other does not.
What people will ask you for
The SIRET is not a document to file away, it is a detail that has to appear.
The law puts your identification number among the Mandatory invoice details of an invoice; in practice it is the SIRET that business clients, supplier portals and the platforms paying you all ask for, because it points to one precise establishment and not merely to a company.
You will be asked for it again when you open a dedicated bank account.
An invoice without a SIRET is not void, but it hands the client a convenient reason to leave it at the bottom of the pile.
The number does not cover everything, though.
A SIRET is not a VAT number. The intra-EU VAT number is a separate identifier, issued by your service des impôts des entreprises, the business tax office, on request and never automatically.
Getting it is entirely free: letters offering to handle it for a fee are selling a service, not an obligation.
Many micro-entrepreneurs have no extrait Kbis (company registration extract) to produce either, since that document comes from the trade register, where liberal professions are not listed.
What you send instead is your SIRENE status notice, downloaded free of charge from the INSEE online service.
The calendar the SIRET does not control
Take a graphic designer who declares her start of activity on 5 March 2026 at the guichet unique, as a non-regulated liberal professional outside the Cipav.
Her number reaches her a few weeks later, and she waits during that time. That is the mistake: the clocks started on 5 March.
The ACRE claim must be filed within 60 days of the start date declared, so by 4 May 2026 at the latest, or the relief is lost for good.
Her contributions, meanwhile, are calculated on what she collects and not on what arrived in the post: on 3,000 € collected in 2026 from liberal services taxed as BNC (non-commercial profits), the full rate is 25.6% in 2026, or 768 € of social contributions.
Filing that claim in time halves the bill: a business started up to 30 June 2026 pays 12.8% in 2026 while the relief lasts, or 384 € on the same collections, and here the Acre runs until the end of the third calendar quarter following the one in which the activity began, so until 31 December 2026.
A business started from 1 July 2026 pays 19.2% in 2026 instead.
As for the vocational training contribution, 0.2% for a liberal profession in 2026, the Acre never covers it: it falls due once a positive turnover has been declared in the previous calendar year.
Receiving your SIRET does not start the CFE clock. For a micro-entrepreneur with no employees, the year of creation for CFE purposes is the first year the business records any turnover, as the official tax doctrine published in the BOFiP sets out.
Registering in October 2026 and issuing a first invoice in January 2027 pushes the first-year exemption to 2027, and the first bill to 2028.
A notice received before the first euro is collected opens the way to a claim for relief (dégrèvement) with the business tax office.
A public number, tied to an address
The SIRENE register is open. Anyone can look your name up in the public business directory and read your SIRET, your code APE and the address you declared.
When the Business address you chose is your own home, still the most common case in a micro-enterprise, the address on screen is your living room.
Your SIRET is public, and so is the address attached to it. INSEE lets you request non-diffusible status, which removes your details from the files it redistributes, through its dedicated online service.
The request can be made at any time, but it does not claw back the copies already harvested by private directories: better to think about it before the first invoice than after the first cold call.
One last point almost nobody sees coming: this number is not granted for life.
A move closes the original establishment and opens another, the NIC changes, so the SIRET changes, while the SIREN stays exactly the same.
That is why a client of three years may still hold an expired number in their invoicing software, and why a change of address is declared at the guichet unique like any other amendment.
Frequently asked questions
What is the difference between a SIREN and a SIRET?
The SIREN has nine digits and identifies the company for its entire life.
The SIRET has fourteen: the SIREN followed by a five-digit NIC identifying the establishment, meaning the trading address.
A company holds one SIREN and as many SIRET numbers as it has establishments open.
What should I do while my SIRET has not arrived?
Keep going, and above all do not let deadlines slip. The ACRE claim runs from the start date declared at the guichet unique, not from the day the number reaches you.
Tell your client the number is on its way, and wait for it before issuing the final invoice if their accounts department insists.
Must the SIRET appear on my invoices?
Put it there every time.
The law requires the company identification number among the mandatory details of an invoice, in the same way as your name and address; business clients and supplier portals, for their part, ask for the SIRET, which is more precise since it points to the establishment.
A quotation follows the same logic, since it often serves as the basis for the purchase order.
Does my SIRET change if I move?
Yes, and that is normal.
The NIC identifies the establishment, meaning the address: moving premises or professional home closes one establishment and opens a new one, with a new SIRET attached.
The SIREN does not move, and your company remains exactly the same one.