ADV-VAT: data quality hint
VAT identifier not in its compact form or not in the format of its country
A data quality hint, not part of the official rules. EN 16931, Peppol BIS, XRechnung and Factur-X have no such rule, so an invoice with this hint can be valid. The validator lists hints in a separate section of the result (and in advisories in the API); they never make an invoice invalid.
What this rule checks
Checks the Seller VAT identifier (BT-31), the Buyer VAT identifier (BT-48) and the Seller tax representative VAT identifier (BT-63). The official rules check only the two-letter prefix (BR-CO-09); a few country rules check more. A VAT identifier with spaces, dots or hyphens, or one without the format of its country, is not found in VIES or in the receiver's master data. The formats are those VIES uses for the EU member states (Greece: EL, Northern Ireland: XI), and the known formats for GB, NO (with MVA) and CH (CHE, optionally with MWST, TVA or IVA; the official notation CHE-123.456.789 MWST is fine too). A field an official rule already reports (NO-R-001, SE-R-001, SE-R-002, GR-R-003) gets no hint. This checks the format only, not whether the number is registered.
How to fix it
Write the VAT identifier in its compact form, the prefix followed by the number without spaces, dots or hyphens (e.g. BE0403170701), and check the number in VIES.
Related rules
Check your invoice
Upload your invoice to check it against the official EN 16931, Peppol BIS, XRechnung or Factur-X rules. The result lists data quality hints such as ADV-VAT in a separate section; they never make an invoice invalid. Free, instant, no signup.