Validation rules

BR-52 — EN 16931 rule

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.

Related rules

• BR-51 — A card payment must never carry the full primary account number (BT-87) — at most the first 6 and last 4…
• BR-53 — A VAT accounting currency (BT-6) is given, so the VAT total in that currency (BT-111) must be present as well.
• BR-50 — A credit-transfer payment account is present but its account identifier (IBAN, BT-84) is empty.
• BR-54 — An item attribute (BG-32) must carry both a name (BT-160) and a value (BT-161).
• BR-49 — Payment instructions (BG-16) are present but the payment means type code (BT-81) is missing.
• BR-55 — A preceding-invoice reference (BG-3) is present but the preceding invoice number (BT-25) is missing.

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.

Or try it live: drop any XRechnung XML on the free validator — same KoSIT-backed report, no account.