What I learned reading ten EU company registers

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. So you can check a supplier, get a green tick, and be looking at an insolvency estate. The national registers know. VIES doesn't ask them. Ten registers, and what each actually gives you I found free, public, machine-readable-enough sources for ten countries: Bulgaria, Czechia, Estonia, Finland, France, Greece, Latvia, Poland, Romania and Slovenia. They are not equivalent, and this is the thing I'd have liked written down somewhere before I started: Six of them report company *state * — inactive, in liquidation, bankrupt, insolvent, terminated, ceased, struck off: Romania, Estonia, France, Greece, Bulgaria, Latvia. This is the valuable one. Three report whether the company is actually VAT-active — Poland, Romania, Slovenia. That matters more than it sounds, because VIES does not distinguish "this is a real company that isn't VAT-registered" from "this number belongs to nobody". The rest give you a name and not much more. Czechia, for instance, is in the ten but in neither of the other two groups. It confirms a name. That's it. Worth knowing before you build a feature around it. Poland is the interesting one Poland is the