Validation rules

UBL-SR-45

The payment due date inside cac:PaymentMeans appears more than once — cbc:PaymentDueDate is allowed at most once in the document.

Rule: UBL-SR-45 — official EN 16931 / XRechnung rule
Severity: error
Business term: BT-9 — Due date
Field in your JSON: invoice.due_date
Detected by: tier 3 — KoSIT validator (authoritative)
Reachability: Only reachable when validating your own XML — normbill-generated documents cannot trigger it

The serializer writes the due date as document-level cbc:DueDate, never as PaymentMeans/PaymentDueDate.

How to fix it

Keep a single PaymentDueDate. In UBL invoices the due date (BT-9) is normally the document-level cbc:DueDate — that is where normbill writes invoice.due_date.

UBL-SR-45 auf Deutsch — was bedeutet der Fehler?

Der KoSIT-Validator lehnt die Rechnung ab, weil das Fälligkeitsdatum innerhalb von cac:PaymentMeans mehrfach vorkommt — cbc:PaymentDueDate ist höchstens einmal erlaubt.

So beheben Sie den Fehler

Behalten Sie höchstens ein PaymentDueDate. In UBL-Rechnungen gehört das Fälligkeitsdatum (BT-9) regulär in das dokumentweite cbc:DueDate — dort schreibt es auch normbill (invoice.due_date).

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.