Calculate a French VAT number from a SIREN
The check key takes one line to compute. Here is the formula, its pitfalls and how to verify the result.
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The formula
A French intra-EU VAT number is made of the FR prefix, a two-digit key and the SIREN.
The key is (12 + 3 × (SIREN modulo 97)) modulo 97. It fits in two digits, padded with a leading zero if needed.
The pitfalls
A well-formed number is not necessarily active: the company may be closed or not liable for VAT.
To check it, query the European Commission's VIES service.