In Europe, being not able to follow the VAT-rules, can be a show stopper to any chopping cart. That's why it just is so important to have the famous "Ubercart style flexibility" also in handling the VAT issues.

Some starting points:

• General about EU (in different languages)
• VAT Invoicing Rules
• VAT in the European Community
• VAT "sitemap"

Maybe...?

Maybe it makes sense, if Ubercart / Ryan will ask directions also directly from EU authorities? (there's a rule in EU that the authorities have to point you to the right direction / to the right office to ask and get helped)

If we're lucky, there's a clear check list for developers to follow...

My 2 centimos from Sunny Spain...