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 (notably France and Germany) expect as audit evidence, alongside an invoice that applied reverse charge. 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 issued against your VAT, not vatnode's — a check run under vatnode's own VAT would be worthless as evidence for your invoice. You don't strictly need it for everyday, non-audit validation. Without a requester configured, every response still includes a checkId and a verifiedAt timestamp, but those are vatnode's own internal reference for the call — useful for looking a specific check up with support, not evidence by themselves. See the VAT audit trail guide for the full picture, including how retention requirements vary by country.