Check an EU VAT number against the VIES database (the EU-wide cross-border VAT validator). Returns valid/invalid + registered name and address if the national database returns them. Accepts either (country_code, vat_number) separately or a combined vat like 'PL5252344078'. For Polish JDG issuing 0% VAT invoices to EU B2B customers: ALSO pass requester_country + requester_vat with your own PL VAT — VIES will return a consultation_number that serves as legal proof of the check. Keep this number for your records. VIES will not issue a consultation number if EITHER VAT is invalid.

List the country codes supported by VIES (all 27 EU member states, plus XI for Northern Ireland).