What it means
The mandate reference (BT-89) identifies the agreement in which the buyer allowed the seller to collect the payment by direct debit. The rule checks that each payment means block (cac:PaymentMeans) holds it at most once, in cac:PaymentMandate/cbc:ID, regardless of the payment method.
Why it matters
The mandate reference links the invoice to the agreement that allows the collection.
How to fix it
In your invoicing software, open the payment or direct debit details and keep a single mandate reference in each payment means block. If the invoice is not paid by direct debit, you can leave the mandate out. In the XML, each cac:PaymentMeans may contain at most one cac:PaymentMandate/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
Mandate reference 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-28 still fails, and which other rules do.
Related rules
- UBL-SR-29 Only one SEPA creditor identifier is allowed in the invoice
- UBL-SR-30 A discount can have only one reason text
- UBL-SR-31 A charge can have only one reason text
- UBL-SR-32 A VAT breakdown row can give only one VAT exemption reason
- UBL-SR-33 A supporting document can have only one description
- UBL-SR-34 Each invoice line can carry only one note