Validation rules

BR-52

An additional supporting document (BG-24) has no document reference (BT-122).

Rule

BR-52 — official EN 16931 / XRechnung rule

Severity

error

Business term

BT-122 — Supporting document reference

Field in your JSON

invoice.supporting_documents[*].id

Detected by

tier 3 — KoSIT validator (authoritative)

Reachability

Not expressible through the normbill invoice model — documented for completeness

The request schema requires supporting_documents[i].id (BT-122); generated XML always writes cbc:ID.

How to fix it

Add cbc:ID to every cac:AdditionalDocumentReference.

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.