What is the VIES consultation number, and do I need it?

It's the EU Commission's requestIdentifier for a specific check — the official EU-side reference some tax authorities expect as audit evidence. It's opt-in: vatnode returns it only when you supply your own EU VAT number as the requester (in the dashboard or via the requesterVat query param), because the identifier is tied to your VAT, not ours. It isn't unique to vatnode — other providers return it too — but you don't need it for everyday validation; the checkId and verifiedAt on every response already give you a timestamped record.