It is possible to check whether a VAT registration number shown on an invoice is valid. This is important because the purchaser cannot recover VAT incorrectly charged by an unregistered trader unless Customs & Excise allow them to do so by concession. Therefore, registration numbers should be tested as follows:
- The first seven digits of the VAT registration number are listed vertically.
- Each digit is multiplied by a number, starting with 8 and decreasing to 2.
- The sum of the multiplications is calculated.
- 97 is subtracted from the sum as many times as is necessary to arrive at a negative number.
- The negative number should be the same as the last 2 digits of the VAT registration number if it is valid.
VAT registration number 339 0727 47
3 *8 = 24
3 *7 = 21
9 *6 = 54
0 *5 = 0
7 *4 = 28
2 *3 = 6
7 *2 = 14
Total = 147
147 - 97 = 50 - 97 = - 47
As the negative number(- 47) is the same as the last two digits of the VAT number, the number is valid.
Courtesy of http://www.2-small-business.com/number_ ... _vat.shtml
Also, you may use the EU site http://ec.europa.eu/taxation_customs/vies/ to verify the registration.