What it means
The invoiced object identifier (BT-18) names the thing the invoice is about, such as a subscription number, a phone number or a meter point. In UBL it is the cbc:ID of a cac:AdditionalDocumentReference whose cbc:DocumentTypeCode is 130. The rule counts only cbc:ID elements in references with that code. Other additional document references, such as supporting documents (BG-24), are not limited by it.
Why it matters
EN 16931 allows one invoiced object identifier per invoice.
How to fix it
In your invoicing software, find the field for the object, subscription or asset the invoice relates to and keep one value. If you also send an attachment or a supporting document reference, check that it is not exported with document type code 130. To mention several objects, list the extra ones in the invoice note. In the XML, keep one cac:AdditionalDocumentReference with cbc:DocumentTypeCode 130 and one cbc:ID.
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
Invoice object identifier 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-04 still fails, and which other rules do.
Related rules
- UBL-SR-05 Payment terms can be given only once
- UBL-SR-06 A preceding invoice reference can name only one invoice
- UBL-SR-07 A preceding invoice reference needs the invoice number
- UBL-SR-08 An invoice can have only one invoice period
- UBL-SR-09 An invoice can have only one seller name
- UBL-SR-10 An invoice can have only one seller trading name