Validation rules
UBL-SR-39
The project reference (BT-11) appears more than once — only one cac:ProjectReference with one cbc:ID is allowed.
- Rule
UBL-SR-39— 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 project reference; generated XML never contains cac:ProjectReference.
How to fix it
Keep a single ProjectReference element in your XML.
UBL-SR-39 auf Deutsch — was bedeutet der Fehler?
Der KoSIT-Validator lehnt die Rechnung ab, weil die Projektreferenz (BT-11) mehrfach vorkommt — nur ein cac:ProjectReference mit einer cbc:ID ist erlaubt.
So beheben Sie den Fehler
Behalten Sie genau ein ProjectReference-Element im XML.
Official sources
- XRechnung specification (KoSIT / xeinkauf.de)
- KoSIT validator on GitHub and the XRechnung validator configuration
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.