Hi,
You could currently add any additional information you like directly in the email body or the attached invoice, but I'm open to adding additional commonly used fields for EU.
Can you clarify about the needed fields and example values and data types. You mentioned tax but is that the tax amount? what is tax code?
For VAT you just want to enter an identification number? I guess that is similar to tax id we have in the US.
Regarding the customer address. I "could" expose those fields but when using PayPal or Google checkout those fields will be populated/overwritten by values provided at the time of payment, ie whatever the person enters for the billing address of their credit card. Similarly with Authorize.NET the user is required to fill in that information and it must match the billing info on the credit card, though we could pre-popualte it, they would be able to change it and would need to make it match the credit card billing address.
Best,
Joe