UBL-SR-28
EN 16931-1 layer: en16931
Checked against Peppol BIS Billing 3.0 2026.5
What does UBL-SR-28 mean? Mandate reference identifier shall occur maximum once
Why did my invoice fail UBL-SR-28?
The Mandate reference identifier (BT-89), in cac:PaymentMeans/cac:PaymentMandate/cbc:ID, is the unique SEPA direct-debit mandate reference agreed between seller and buyer, and it may occur at most once. A single direct-debit mandate applies per invoice, so only one mandate reference is allowed.
Official rule text
Mandate reference identifier shall occur maximum once
Common causes
- More than one cac:PaymentMandate is emitted, each with its own ID.
- The mandate ID is repeated within a single PaymentMandate element.
- A mandate reference is added even though the payment means is not direct debit, colliding with another mapping.
How do I fix it?
Provide one mandate reference: <cac:PaymentMeans>...<cac:PaymentMandate><cbc:ID>MNDT-2026-000123</cbc:ID></cac:PaymentMandate></cac:PaymentMeans> and remove duplicate PaymentMandate/ID entries.
Related rules
UBL-SR-01 · UBL-SR-02 · UBL-SR-03 · UBL-SR-04 · UBL-SR-05 · UBL-SR-06 · UBL-SR-07 · UBL-SR-08
Check your invoice against this rule
Paste it into the live demo, or call POST /v1/validate. See the quickstart.