VAT identification number

A value added tax identification number or VAT identification number (VATIN) is an identifier used in many countries, including the countries of the European Union, for value added tax purposes.

In the EU, a VAT identification number can be verified online at the EU's official VIES website. It confirms that the number is currently allocated and can provide the name or other identifying details of the entity to whom the identifier has been allocated. However, many national governments will not give out VAT identification numbers due to data protection laws.

The full identifier starts with an ISO 3166-1 alpha-2 (2 letters) country code (except for Greece, which uses the ISO 639-1 language code EL for the Greek language, instead of its ISO 3166-1 alpha-2 country code GR) and then has between 2 and 13 characters. The identifiers are composed of numeric digits in most countries, but in some countries they may contain letters.

Foreign companies that trade with non-enterprises in the EU may have a VATIN starting with "EU" instead of a country code.

BTW-nr Mwst-nr

The French key is calculated as follow : Key = [ 12 + 3 * ( SIREN modulo 97 ) ] modulo 97, for example  : Key = [ 12 + 3 * ( 404,833,048 modulo 97 ) ] modulo 97 = [12 + 3*56] modulo 97 = 180 modulo 97 = 83 so the tax number for 404,833,048 is FR 83,404,833,048 source from : www.insee.fr

'IE'+7 digits and two letters, e.g. IE1234567FA (since January 2013, see [2])
'IE'+one digit, one letter/"+"/"*", 5 digits and one letter (old style, currently being phased out, see [3])

For individual persons / freelancers, its either 'ES'+8 digits+letter (for Spaniards) or 'ES'+letter+7 digits+letter (for foreigners). e.g. ES99999999R

For the 9-digit scheme, the 2-digit block containing the 8th and 9th digits is always in the range 00 to 96 and is derived from a weighted modulus-97 check number (an identical algorithm is used for the 12-digit scheme, ignoring the extra 3-digit block). The current modulus-97 series ran out during 2010, so a parallel series of numbers was introduced from November 2009 for new registrations, restarting at 100 nnnn nn and following the same format but with the last two digits derived from an alternative algorithm known as "9755". The algorithm is identical to the one for the established series except that 55 is subtracted to give the check number (modulus 97), so the check number is either 55 less than or (if this would be negative) 42 greater than the check number that a VAT number in the established series would have if it were identical in the first seven digits. The details of the 97−55 check algorithm were to be secret but are now available from HMRC on request.

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Wikipedia