Validate an EU VAT number against the official VIES registry before invoicing, onboarding or a reverse charge. Per-country syntax is checked locally first, so invalid formats never touch the network. Valid numbers return the registered company name and address when disclosed, plus an optional consultation number (requesterVat). Never a false 'invalid': if VIES is down you get a 503 and are not charged. ?attest=1 → Ed25519-signed.

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