What it means
A supporting document reference (BG-24) points to a document that backs up the invoice, such as a timesheet or an attached file. It has a reference (BT-122) and may have a description (BT-123), and the description may appear only once for each supporting document. The rule checks each cac:AdditionalDocumentReference for at most one cbc:DocumentDescription.
Why it matters
The description tells the reader what the document is.
How to fix it
In your invoicing software, check the attachments or supporting documents and keep at most one description for each. Remove the extra text or join the two into one. In the XML, each cac:AdditionalDocumentReference may hold only one cbc:DocumentDescription.
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
Supporting document description 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-33 still fails, and which other rules do.
Related rules
- UBL-SR-34 Each invoice line can carry only one note
- UBL-SR-35 A line can refer to only one purchase order line
- UBL-SR-36 A line can have only one invoice line period
- UBL-SR-37 A line can have only one price discount
- UBL-SR-39 An invoice can have only one project reference
- UBL-SR-40 The buyer can have only one trade name