+After installing this module, values entered in the VAT field of Partners will
+be validated for all supported countries. The country is inferred from the
+2-letter country code that prefixes the VAT number, e.g. ``BE0477472701``
+will be validated using the Belgian rules.
+
+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.