How accurate is the validation?

vatnode queries the official VIES database in real time, so accuracy is as good as the EU system itself: when VIES says "valid", the number was registered and active at the exact moment of the check. Some member states update their registrations closer to real time than others, so a very recent change may take a day or two to appear. Valid results are cached for 15 minutes for speed — the cacheHit field on every response tells you whether an answer was fresh or served from cache. If you've set your own EU VAT as the requester in dashboard Settings, caching is bypassed automatically so every check gets a fresh VIES lookup; see the validation endpoint reference for the exact behavior.