Check a customer’s SIREN before you invoice
Type the nine digits: the tool checks the key and works out the EU VAT number that follows from it, without querying any register.
This SIREN is
Well formed
The check digit is right. Then check that the business exists and is in the directory.
| SIREN | 404 833 048 |
| Derived EU VAT number | FR83404833048 |
| Where it goes on the invoice | Customer block, item 1° |
Format check only, done in your browser; no register is queried.
Prepared by Radif Partners · Method · Tax code, BOFiP and approved-platform list checked on 25 October 2026
The customer’s SIREN number becomes a mandatory invoice mention with the reform, under item 1° of article 242 nonies A of annex II to the French tax code. It is the number the approved platform uses to find your customer in the directory and route the invoice, and the one the administration uses to match the sale with the purchase. A SIREN has nine digits, the last of which is a check digit computed with the Luhn algorithm: if one digit is wrong or two digits are swapped, the check no longer matches. The French EU VAT number follows from the SIREN: FR, then a two-digit key equal to twelve plus three times the remainder of the SIREN divided by 97, all modulo 97, then the nine digits. The tool does both calculations in your browser. It does not tell you whether the business exists or is active: for that, check the official directory or the Insee register before issuing an important invoice.
Why the customer SIREN becomes mandatory
E-invoicing relies on automatic routing. Your platform does not know your customer’s electronic address: it queries the e-invoicing directory with the SIREN, which returns the platform that customer chose. Without a SIREN, or with a wrong one, the invoice cannot find its recipient. That is why article 242 nonies A of annex II to the French tax code adds the customer SIREN to the mandatory mentions, and why the platform must check that the number exists, its format and its validity before transmitting.
How the check digit works
Read the nine digits from right to left. Keep the first as it is, double the second, keep the third, double the fourth, and so on. When a doubled digit exceeds nine, subtract nine. Add everything up: the SIREN is well formed if the total is a multiple of ten. With the number 404 833 048, often used as an example, the total works out, and the derived VAT number is FR83404833048.
| Check | What it catches | What it misses |
|---|---|---|
| Nine digits | One digit too many or too few | A wrong number altogether |
| Luhn key | A typo, two neighbouring digits swapped | An invented but well-formed number |
| Directory | Whether the customer can receive, and via which platform | Anything else about the business |
This SIREN is
This SIREN is
Well formed
| SIREN | 987 654 324 |
| Derived EU VAT number | FR14987654324 |
| Where it goes on the invoice | Customer block, item 1° |
Organising the collection
The simplest approach is to ask each new customer for their SIREN at the quote stage and to complete your file for existing customers before your mandatory issuing date. Consumers have none, and that is fine: their sales fall under e-reporting, with no e-invoice. Next, the list of new mentions shows where the number goes, and the directory page explains how to check that a customer can receive.
Your own SIREN too
The reform does not only ask for the customer’s number: your SIREN appears in the header of every invoice and serves as your identifier with your platform. Check that it is the same everywhere, on quotes, invoices, your website and your directory entry. A business under the basic exemption, which does not always have a VAT number, uses its SIREN as its tax identifier in the XML file of its invoices, which the creator on this site does automatically.