Nothing is easier Once you have created your account, go to your account My account.

1. Go to Addresses menu.
   
   
2. Update an existing address via the Update option under the address in question or create a new address via the Create new address option.
   
   
3. Fill in/Modify/Delete the VAT number field.
   Make sure that the VAT number follows a certain format : a prefix of two capital letters representing the country (BE/FR/LU/NL) followed by the 10 digits of the identification number, all without SPACE and without DOT.
   
   
4. Save via the Save button.