EU VAT Number Format Check

Validates the format of an EU VAT number (VAT ID, USt-IdNr, reverse charge) against the European Commission's published format table: 27 member states plus GB and XI. Format only, never validity - no VIES call, and the response says so. Reports every published pattern with its match status, enforces note 4 for ES, honours case sensitivity, and names the source's own contradictions: BE prints two patterns while note 2 denies one, RO prints nine digits while its description allows two to ten.