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 once you set your own EU VAT number as the requester in dashboard Settings, because the identifier is tied to your VAT, not ours. You don't need it for everyday validation, though — the checkId and verifiedAt on every response already give you a timestamped record.