A French supplier sends an invoice and your finance team asks for "the SIRET". You get a number back: sometimes nine digits, sometimes fourteen, occasionally both, and nothing tells you which is which. Is the long one the company, or the office you have been dealing with? Is it even real? Every answer you find online repeats the same definition and stops there.
This page does the three things that definition leaves out: it reads a SIRET digit by digit, it shows the free official routes to find a given company's number, and it maps the French identifier onto the one you already know in ten countries — including the two check-digit rules that make ordinary validators reject real, live businesses.
Two numbers, two objects: the company and the site
The SIREN identifies the company. The SIRET identifies one place where that company operates. A business holds a single SIREN and as many SIRETs as it has establishments. The first never changes; the second set opens and closes as premises come and go.
The acronyms say exactly that. SIREN stands for Système d'identification du répertoire des entreprises — the registry of enterprises — and "il est composé de 9 chiffres", nine digits. SIRET stands for Système d'identification du répertoire des établissements, the registry of establishments, "composé de 14 chiffres" (French public administration, entreprendre.service-public.gouv.fr). The national statistics institute that issues them — INSEE, the Institut national de la statistique et des études économiques — defines the SIREN as "a nine-figure identifier attributed to each legal unit" (INSEE, Siren number).
The practical consequence shows up the moment you work with a list rather than a single company. Two rows carrying the same SIREN are the same legal entity, however differently the trading name is spelled. Two SIRETs under that SIREN are two addresses. That is the only reliable way to deduplicate a file of establishments without comparing text strings.
Reading a SIRET digit by digit
A SIRET splits into two blocks. The first nine digits are the company's SIREN. The next five are the NIC, the numéro interne de classement attached to that specific establishment. The final digit of each block carries no information: it is a check digit, which French paperwork calls the chiffre de contrôle. The neighbouring vocabulary is worth learning at the same time, because official extracts never translate it: numéro SIREN and numéro SIRET for the identifiers, siège social for the registered office, établissement secondaire for a branch, and état administratif for the open-or-closed flag.
INSEE spells out the mechanics: the SIRET "is split into two parts: the first is the Siren number of the legal unit to which the Siret unit belongs; the second is usually called the NIC (internal classification number), and is made up of a four-figure number attributed to the establishment and a control figure used to validate the Siret number as a whole" (INSEE, Siret number). On the SIREN side, "the ninth figure is a control figure to validate the number".
So a SIRET stripped of its last five digits is not a "short SIRET" — it is a SIREN. And a SIREN padded with five arbitrary digits will only pass the check by accident, precisely because of the control figure that closes the NIC.
The Luhn key, and the one French case where it fails
You can verify a French identifier offline, with arithmetic alone. "Les numéros SIREN, NIC et SIRET intègrent le mécanisme de contrôle de parité connu sous le nom de formule (ou clé) de Luhn" — SIREN, NIC and SIRET numbers all embed the Luhn parity check, states INSEE's technical documentation (INSEE, economic identifiers). A number that fails Luhn has usually been mistyped.
Usually. La Poste, the French postal operator, is the exception that breaks naive validators. All of its branches share the SIREN 356 000 000, and the public company search API listed 8,919 of them still open on 28 July 2026. Take four of its branches in the 15th arrondissement of Paris, exactly as the Annuaire des Entreprises publishes them — 35600000041443, 35600000041452, 35600000041457, 35600000041461. Not one passes the Luhn check. The plain sum of their digits, however, is a multiple of 5 every time.
A validator that applies Luhn alone therefore rejects thousands of entirely genuine establishments, all belonging to the same operator. If you are checking numbers at scale, the rule to implement is: Luhn first, and for SIREN 356 000 000 only, fall back to the digit-sum test.
Finding a French company's number: three routes
This data is public and free. Which route you take depends on what you start from: the company name, the address of its website, or a whole list to process at once. None of the three requires an account or a payment.
From the name or the address. The Annuaire des Entreprises, run by the French interministerial digital directorate (Direction interministérielle du numérique), searches by company name, address, director or number, and returns the SIREN, the head-office SIRET and the list of establishments. It is the official entry point, fed by INSEE, INPI, Urssaf and tax administration data.
From the company's website. A French commercial website publishes the number in its mentions légales, the legal notice page. That is the fastest route when you already have the URL, and the one our legal-identifier enrichment takes: it reads the SIRET off the legal notice, runs the Luhn check so a phone number is never mistaken for a SIREN, and keeps the exact source URL alongside the result.
From a whole list. Record-by-record lookup stops working somewhere around the hundredth row. The public company search API answers without an access key, and matching name and address against the répertoire Sirene also returns legal form, activity code, headcount band and directors for the rows that have no website at all. If you want to try that step on your own file, the free alpha is open on /demander-acces.
One reflex worth acquiring: when a company has several establishments, there is no single "correct" SIRET in the abstract. The SIRET of the registered office — the siège — identifies the legal entity; the SIRET of an établissement bills or reaches the right site. Ask which one is wanted before you send anything.
What a SIRET does not tell you
Three misunderstandings come up again and again, and each one costs time. A SIRET is not a VAT number, it is not evidence that a business is still trading, and it carries no weight outside France.
The French intra-EU VAT number — numéro de TVA intracommunautaire — is built on the SIREN, not the SIRET: FR, then a two-digit key, then the nine digits of the SIREN. The key is computed, not guessed — the arithmetic is set out on our page about SIRET, SIREN, VAT and RCS enrichment.
A valid SIRET also says nothing about actual activity. A closed establishment keeps its number; the état administratif field records whether it is open or closed, and you have to read that field separately. That belongs to data enrichment rather than to format validation.
Finally, the SIRET is a French identifier, issued within the répertoire Sirene maintained by INSEE. A foreign company with no French establishment simply is not in it, and asking such a company for a SIRET makes no sense: it carries the number issued by its own national register.
The SIREN equivalent in ten countries
No country reproduces the SIREN/SIRET pair exactly. Most have a single company identifier, issued either by a commercial register or by the tax administration. Belgium is the only one in the table below that separates the entity from each of its premises, the way France does.
| Country | Identifier that plays the SIREN role | Who issues it |
|---|---|---|
| Belgium | Numéro d'entreprise (10 digits), plus a number per unité d'établissement | Crossroads Bank for Enterprises |
| United Kingdom | Company registration number (8 characters) | Companies House |
| Ireland | Company number | Companies Registration Office |
| Netherlands | KVK-nummer | Kamer van Koophandel |
| Germany | Handelsregisternummer (HRA / HRB), tied to the registering court | The competent Registergericht |
| Spain | NIF | Agencia Tributaria, with incorporation recorded at the Registro Mercantil |
| Italy | Codice fiscale / partita IVA, completed by the REA number | Agenzia delle Entrate and the chambers of commerce |
| Portugal | NIPC | Registo Nacional de Pessoas Coletivas |
| Switzerland | Enterprise identification number (UID / IDE) | Federal Statistical Office |
| United States | State entity number, alongside the federal EIN | Each state's Secretary of State; the IRS for the EIN |
Three traps hide in that table. First, a tax identifier is not a register identifier. The American EIN is described by the tax authority as "a federal tax ID number for businesses, tax-exempt organizations and other entities" (IRS, Employer ID numbers) — it proves tax registration, not incorporation, which happens at state level. The same caution applies to the Spanish NIF.
Second, formats vary inside a single country more than you would expect. A Companies House number is "an 8 digit number or 2 alpha characters followed by a 6 digit number" (GOV.UK, HMRC COTAX manual): a validator that accepts eight digits only will reject Scottish and Northern Irish companies.
Third, identifiers age. In Belgium the enterprise number "se compose de 10 chiffres", ten digits, and since the range beginning with 0 ran out, "un premier numéro d'entreprise commençant par 1 a dès lors été attribué le 19 septembre 2023" — the first number starting with 1 was issued on 19 September 2023 (Belgian Federal Public Service Economy). A validation rule written before that date now rejects newly incorporated companies. For where to look each register up, our guide to company-register equivalents country by country lists the official service for each one.
Across the EU, the cross-border identifier already exists: the EUID
Asked for the international equivalent of a SIRET, most sources answer "the DUNS number". For any legal purpose that is wrong: the DUNS is assigned by a private business-information company. It identifies; it does not constitute a register entry.
The real answer, at European scale, is the EUID. Since June 2017 the commercial registers of every EU country have been interconnected through BRIS, reachable via the "Find a company" service of the e-Justice portal (European Commission, e-Justice portal). Every registered company carries a unique identifier built by concatenating the country code, the identifier of its register and its national registration number. For a French company, the national number inside that EUID is its SIREN.
That is the point to keep if you build company lists across several countries: the "identifier" column does not hold the same thing from one row to the next, and it is safer to name it per country than to treat it as one homogeneous field. A list assembled from establishments collected area by area attaches afterwards to national registers, not to a worldwide identifier that does not exist. The rest of the vocabulary is gathered in our prospecting glossary, and the French sources are detailed in our page on company databases in France.
FAQ — SIRET, SIREN and their equivalents
What exactly is the difference between SIREN and SIRET?
The SIREN has 9 digits and identifies the company; the SIRET has 14 and identifies one of that company's establishments. A SIRET always starts with the SIREN, followed by 5 digits specific to the site, called the NIC (numéro interne de classement). One company, one SIREN, as many SIRETs as it has premises.
How do I find a French company's SIRET from its name?
Through the Annuaire des Entreprises, the free public service run by the French interministerial digital directorate: it searches by name, address, director or number, and returns the SIREN, the head-office SIRET and the list of establishments. The legal notice page of the company's own website carries the same information.
Can a real SIRET fail the Luhn check?
Yes, for the establishments of La Poste, all attached to SIREN 356 000 000. Their SIRETs do not satisfy the Luhn key; the sum of their digits is a multiple of 5 instead. A validator that ignores this exception rejects thousands of open branches.
Is the SIRET the same as the company's VAT number?
No. The French intra-EU VAT number is written FR, plus a two-digit key, plus the 9 digits of the SIREN — not the SIRET. And a valid SIRET does not by itself mean the business is VAT-registered.
What is the SIRET equivalent in Belgium and in Portugal?
In Belgium the 10-digit enterprise number plays the SIREN role and the establishment-unit number plays the SIRET role: it is the system closest to the French one. In Portugal the equivalent is the NIPC, issued by the Registo Nacional de Pessoas Coletivas; there is no per-establishment number.
Can a foreign company have a SIRET number?
Only if it operates an establishment in France, in which case that site is registered in the répertoire Sirene like any other. Without a French presence, a company has no SIRET: it carries the identifier of its own national register.