VAT key
key = (12 + 3 × (SIREN mod 97)) mod 97
French VAT number calculator
Build the intra-community VAT number of a French company (FR + key + SIREN) from its SIREN or SIRET, or check the key of an existing number, right in your browser.
- France
9 digits (SIREN) or 14 digits (SIRET): only the first 9 are used.
French number: FR, 2 key characters, then the 9 digits of the SIREN. Spaces are accepted.
- Key
- SIREN
The calculation rebuilds the mathematical form of the number. It does not prove that the company is registered for VAT or that its number is active: only the European Commission’s VIES service confirms that. Nothing is sent from this tool.
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How does this tool work?
In France, the intra-community VAT number is made of the country code FR, a 2-digit computer key and the company’s SIREN number (9 digits). It must appear on invoices between businesses in the European Union. This tool calculates the key and rebuilds the full number from a SIREN or SIRET, or checks that an existing FR number matches its SIREN. It also checks the SIREN’s own key to catch a typo from the start. It is useful for anyone invoicing or auditing a French customer or supplier, inside or outside France.
If you enter a SIRET (14 digits), the tool keeps its first 9 digits: that is the SIREN, which identifies the company. The last 5 digits (NIC) identify the establishment and are not part of the VAT number.
The tool takes the remainder of the SIREN divided by 97, multiplies it by 3, adds 12, then takes the remainder of the division by 97 again. The result, written on two digits, is the key.
The VAT number is FR + key + SIREN, for example FR 27 552 032 534.
In check mode, the tool recalculates the key from the 9 SIREN digits and compares it with the key of the number entered. It also checks the SIREN with the Luhn formula described by INSEE, the French statistics institute.
How to use this tool
Choose the action
Calculate a number from a SIREN or SIRET, or check an FR number you already have.
Enter the identifier
Type the SIREN, SIRET or VAT number, with or without spaces.
Check the result
Read the formatted number, the key and the SIREN status, then confirm on VIES that the number is active.
Key of the French VAT number
Full number
VAT number = FR + key (2 digits) + SIREN (9 digits)
- SIREN
- 9-digit company identifier (the first 9 digits of the SIRET)
- mod 97
- remainder of the integer division by 97
The SIREN carries its own check digit: according to INSEE, doubling every second digit from the right (adding the digits of two-digit results) and summing everything must give a multiple of 10 (Luhn formula).
Use cases
Complete an invoice
Find the VAT number of a French business customer when you only know its SIREN, so you can print it on an intra-community invoice.
Clean a customer or supplier file
Spot mistyped French numbers before an EC sales list, an accounting import or an e-invoicing rollout.
Check a number you received
A French supplier sends you its number: check that it is consistent first, then that it is active on VIES before the first transaction.
Examples
Number calculated from a SIREN
552032534 divided by 97 leaves a remainder of 5. The key is (12 + 3 × 5) mod 97 = 27.
Input
SIREN or SIRET: 552 032 534Result
Intra-community VAT number calculated: FR 27 552 032 534; key: 27Same result from a SIRET
Only the first 9 digits count: 404833048 mod 97 = 56, and (12 + 3 × 56) mod 97 = 180 mod 97 = 83.
Input
SIREN or SIRET: 404 833 048 00022Result
Intra-community VAT number calculated: FR 83 404 833 048Wrong key
A difference of one on the key is enough to make the number inconsistent with its SIREN.
Input
Intra-community VAT number: FR 28 552 032 534Result
Wrong key: the expected key for this SIREN is 27.Tips and best practices
- Always check a new customer or supplier number on VIES: a well-formed number may be inactive or may never have been issued.
- A French business under the VAT franchise scheme normally has no intra-community VAT number unless it requested one for cross-border trade.
- If the SIREN fails the Luhn formula, find the typo before calculating the VAT number.
- Do not confuse this number with VAT amounts: to go from a net to a gross price, use a VAT calculator.
Sources and references
Frequently asked questions
How do you calculate a French VAT number from the SIREN?
Take the remainder of the SIREN divided by 97, multiply it by 3, add 12 and keep the remainder of the division by 97: that is the two-digit key. The number is written FR, then the key, then the SIREN. For example, SIREN 552 032 534 gives FR 27 552 032 534.
Is a calculated number a valid VAT number?
It is mathematically consistent, but that does not prove it was issued or is active. The number is issued by the company’s tax office; check that it is active on VIES, the European Commission’s service, before a transaction.
Can I use the SIRET instead of the SIREN?
Yes. The SIRET starts with the SIREN, followed by 5 digits for the establishment. The tool keeps the first 9 digits, so every establishment of the same company has the same VAT number.
Where does the key formula come from?
The official French government page states that the key has 2 digits without detailing how it is calculated. The formula (12 + 3 × (SIREN mod 97)) mod 97 is the one issued numbers follow and that accounting and invoicing software uses.
Why does the tool reject a German or Belgian number?
Each country has its own VAT number structure. This calculator only handles French numbers; for other countries, use VIES directly, which queries the national tax administrations.
My VAT number has letters in the key, is that normal?
The French format allows letters in the two key characters. In that case the key cannot be calculated with the formula: the tool recognises the format, and only VIES can confirm the number.
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