There are two different levels of VAT number validation:

• By default, a simple off-line check is performed using the known validation rules for the country, usually a simple check digit. This is quick and always available, but allows numbers that are perhaps not truly allocated, or not valid anymore.

• When the “VAT VIES Check” option is enabled (in the configuration of the user’s Company), VAT numbers will be instead submitted to the online EU VIES database, which will truly verify that the number is valid and currently allocated to a EU company. This is a little bit slower than the simple off-line check, requires an Internet connection, and may not be available all the time. If the service is not available or does not support the requested country (e.g. for non-EU countries), a simple check will be performed instead.

Supported countries currently include EU countries, and a few non-EU countries such as Chile, Colombia, Mexico, Norway or Russia. For unsupported countries, only the country code will be validated.