The Magento VIES Module adds fields to Magento's customer profile for European VAT number support. It also provides a two level VAT number validation. The first validation is syntactic. The second uses the VAT Information Exchange System (VIES)'s Web Service. The information about the validity of the VAT number is also stored as read-only fields in the customer profile.

Please note that this project is dead, there is no active development. Feel free to visit the discussion group if you need guidance with the code or if you are interested in taking ownership of the project.