Validate an EU VAT number (VIES)

Validate an EU VAT number against VIES (the European Commission's VAT Information Exchange System) and return the registered trader name and address when valid. Covers the 27 EU member states plus XI (Northern Ireland); Greek numbers use the EL prefix, and GB VAT is out of scope post-Brexit. Live official lookup — when a member-state registry is temporarily down it returns 503 (retryable) rather than reporting the VAT as invalid. Costs 1 credit. When VIES says a Spanish or German number is valid but withholds the name, registry_match {company_id, company_name, address, register} names the company our register holds under that number: register data, not VIES confirmation.