Peppol BIS Billing 3.0 · rule

UBL-CR-134

Layer en16931·Checked against Peppol BIS Billing 3.0 2026.5

What does UBL-CR-134 mean? A UBL invoice should not include the ProjectReference UUID

Why did my invoice fail UBL-CR-134?

The invoice should not contain the element cac:ProjectReference/cbc:UUID, i.e. a UUID on the project reference. This is one of the EN 16931 "cardinality restriction" (UBL-CR) warnings: the UBL 2.1 schema allows the element, but it maps to no business term in the EN 16931 core invoice model, so a compliant core invoice must leave it out. The project reference in EN 16931 consists solely of the identifier BT-11 (cbc:ID); a UUID has no corresponding business term. Receivers may ignore or reject data carried in such elements, so remove it or move the information to the supported business term.

Official rule text

A UBL invoice should not include the ProjectReference UUID

Common causes

Your invoice generator emits the full UBL 2.1 structure and populates cbc:UUID even though EN 16931 does not use it
Mapping from an internal/ERP data model copies every available field into the UBL output instead of only the EN 16931 business terms
A template or example invoice from a non-EN 16931 UBL context (e.g. generic UBL samples) was reused without stripping unsupported elements

How do I fix it?

<cac:ProjectReference>
  <cbc:ID>PROJ-2026-014</cbc:ID>
</cac:ProjectReference>

Check your invoice against this rule

Paste it into the live demo, or call POST /v1/validate. See the quickstart.