Validation rules

UBL-SR-52

An invoice line carries more than one cac:DocumentReference — the line-level invoiced-object identifier (BT-128) is allowed at most once.

Rule: UBL-SR-52 — official EN 16931 / XRechnung rule
Severity: error
Detected by: tier 3 — KoSIT validator (authoritative)
Reachability: Only reachable when validating your own XML — normbill-generated documents cannot trigger it

The normbill invoice model has no line document reference; generated lines never contain cac:DocumentReference.

How to fix it

Keep a single DocumentReference per invoice line.

UBL-SR-52 auf Deutsch — was bedeutet der Fehler?

Der KoSIT-Validator lehnt die Rechnung ab, weil eine Position mehrere cac:DocumentReference-Elemente trägt — die Objektkennung auf Positionsebene (BT-128) ist höchstens einmal erlaubt.

So beheben Sie den Fehler

Behalten Sie genau eine DocumentReference je Rechnungsposition.

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.