Validation rules

BR-CO-09

A VAT identifier (seller BT-31, buyer BT-48, or tax representative BT-63) does not start with an ISO 3166-1 country prefix (Greece uses EL).

Rule: BR-CO-09 — official EN 16931 / XRechnung rule
Severity: error
Business term: BT-31 — Seller VAT identifier
Field in your JSON: invoice.seller.vat_id
Detected by: tier 3 — KoSIT validator (authoritative)
Reachability: Triggerable from your request JSON (generate & validate)

normbill's tier-1 syntax check (NB-VAT-ID-FORMAT) currently covers German ids only; ids with other or missing prefixes are checked by the KoSIT validator.

How to fix it

Prefix the VAT identifier with its issuing country, e.g. "DE123456789" instead of "123456789".

BR-CO-09 auf Deutsch — was bedeutet der Fehler?

Eine Umsatzsteuer-Identifikationsnummer (Verkäufer BT-31, Käufer BT-48 oder Steuervertreter BT-63) beginnt nicht mit einem ISO-3166-1-Länderpräfix (Griechenland verwendet EL).

So beheben Sie den Fehler

Stellen Sie der USt-IdNr. das Ausstellungsland voran, z. B. "DE123456789" statt "123456789".

Official sources

Every 422 from the API lists the rule id, the path in your request JSON, a plain-language message and a suggested fix — see the docs overview for the report format.

Or try it live: drop any XRechnung XML on the free validator — same KoSIT-backed report, no account.