Validation rules

BR-02 — EN 16931 rule

The invoice number (BT-1) is missing or empty.

Rule: BR-02 — official EN 16931 / XRechnung rule
Severity: error
Business term: BT-1 — Invoice number
Field in your JSON: invoice.number
Detected by: tier 3 — KoSIT validator (authoritative)
Reachability: Only reachable when validating your own XML — normbill-generated documents cannot trigger it

The request schema requires invoice.number (BT-1), so generated documents always carry it.

How to fix it

Set a non-empty cbc:ID directly under the invoice root.

BR-02 auf Deutsch — was bedeutet der Fehler?

Die Rechnungsnummer (BT-1) fehlt oder ist leer.

So beheben Sie den Fehler

Setzen Sie eine nicht-leere cbc:ID direkt unter der Rechnungswurzel.

Related rules

BR-01 — The specification identifier (BT-24) is missing — the document does not say which e-invoicing specification…
BR-03 — The issue date (BT-2) is missing or empty.
BR-04 — The invoice type code (BT-3) is missing.
BR-05 — The invoice currency code (BT-5) is missing.
BR-06 — The seller name (BT-27) is missing or empty.
BR-07 — The buyer name (BT-44) is missing or empty.

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.