What it means
Inside a line (BG-25), the document reference carries the line object identifier (BT-128), an identifier for an object the line is based on. A line can have at most one cac:DocumentReference. The check applies to credit note lines too.
Why it matters
EN 16931 has one field for this identifier per line.
How to fix it
In your invoicing software, look at the line for extra object or document references and remove the extras. If you build the XML yourself, keep one cac:DocumentReference in each cac:InvoiceLine or cac:CreditNoteLine. References to supporting documents belong at the top of the invoice in cac:AdditionalDocumentReference, not on the line.
Once the file is corrected, check it again for free: Validate an invoice against EN 16931
Or fix the invoice in a form and download the corrected file, for 1 credit: Fix a rejected e-invoice
The rule as published
Document reference shall occur maximum once Where this rule applies
| Rule set | Version |
|---|---|
| EN 16931 (UBL) | 1.3.17 |
| EN 16931 (UBL credit note) | 1.3.17 |
| XRechnung 3.0 (UBL) | 3.0.2 |
| XRechnung 3.0 (UBL credit note) | 3.0.2 |
| Peppol BIS Billing 3.0 (invoice) | 2026.5 |
| Peppol BIS Billing 3.0 (credit note) | 2026.5 |
| SI-UBL 2.0 / NLCIUS (invoice) | 2.0.3.13 |
| SI-UBL 2.0 / NLCIUS (credit note) | 2.0.3.13 |
| France CTC (UBL invoice) | 1.4.0-04 |
| France CTC (UBL credit note) | 1.4.0-04 |
| CIUS-RO UBL Invoice 1.0.9 | 1.0.9 |
| CIUS-RO UBL Credit Note 1.0.9 | 1.0.9 |
Check your file
Drop your e-invoice to see whether UBL-SR-52 still fails, and which other rules do.
Related rules
- UBL-SR-53 Tax scheme entries need both a scheme code and a number
- UBL-SR-54 An invoice can have only one payment card account
- UBL-SR-55 An invoice can have only one direct debit mandate
- UBL-SR-56 An invoice can have only one tender or lot reference
- UBL-SR-57 Each party can have only one legal registration block
- UBL-SR-58 Bank branch details need one identifier per payment means block