It would be great if this mod could add a VAT number field that is automatically
validated by the official checker at http://ec.europa.eu/taxation_customs/vies/
If the customer is a company within the EU and has a valid VAT number the VAT
would be 0%.
For customers outside the EU or without a valid VAT number, or within the same
country, the VAT would be 21%
Can you make this?

Let me know if I can be of any help.
Kind regards from The Netherlands.