I built a free tool that checks a supplier before you pay them. The part that took most of the work, and taught me most, was reading ten national company registers instead of relying on the EU's own VIES service.
This is what I found out, mostly so the next person doesn't have to.
The problem with "the VAT number is valid"
VIES — the European Commission's VAT Information Exchange System — answers one question: is this VAT number currently registered. That sounds like the question you want answered. It isn't.
A company that has gone into liquidation keeps a cleanly resolving VAT number in VIES. So does one that has been struck off the register. Deregistration and insolvency are run by different authorities on different timetables, and the gap between "this company has stopped being a going concern" and "the VAT number stops validating" can be months.
