A European law defines that unless you can prove that a company has a valid VAT registration in their country, full VAT must be charged om selling products or services between European countries.
It is therefore necessary to validate each company VAR registration number.
Bron : Aphorisms about Microsoft Dynamics NAV
You can specify a format for the VAT Registration number for a Customer, Vendor, Bank or Contact account. So, if you enter a VAT Registration number that is not according to the format specified, the system will return a message error like this:
Bron : Dynamics NAV Messages