Managing Strict VAT ID Validation on Order Total Modules and Testing VAT ID per Country Settings
Note: This manual is for osCommerce v4.
After you accessed the admin area of your website click on Modules and Order structure tabs. Then click on Tax option. If you click on Edit button you can make Strict VAT ID validation either true or false (in this way you can accept only VAT-ID validate via europa.eu web service without trusting the country code with some 8-12 digits).
Regardless of the Strict VAT ID validation described above and before it is executed VAT ID is tested based on the following country settings, for example for Ireland they are:
Vat ID Code Prefix – IE, Vat Code Type – alphanumeric, Vat Code Chars – 8
Note: Different number of symbols can be used in Vat Code Chars field depending on the following information: https://en.wikipedia.org/wiki/VAT_identification_number
'IE'+7 digits and one letter, optionally followed by a 'W' for married women, e.g. IE1234567T or IE1234567TW
'IE'+7 digits and two letters, e.g. IE1234567FA (since January 2013, see )
'IE'+one digit, one letter/"+"/"*", 5 digits and one letter (old style, currently being phased out, see )