Reference

BR-52 Additional supporting document must have a reference

Each Additional supporting document (BG-24) shall contain a Supporting document reference (BT-122).

This is an EN 16931 core rule. The reference (BT-122) lets the buyer match an attachment or external link, such as a timesheet, delivery note or statement, to the invoice. BR-52 checks that the reference is not empty; a missing cbc:ID in UBL is already rejected by the schema. The error appears when a file is attached or linked by URL but only a description or file name is exported.

Solution

Fill cbc:ID in each cac:AdditionalDocumentReference (CII: ram:AdditionalReferencedDocument/ram:IssuerAssignedID) that carries or references a supporting document, for example with the timesheet or delivery note number.

Quick actions

Validate XML Convert invoice

Valid Examples

BT-122 = "TIMESHEET-2026-02" for an attached timesheet

Invalid Examples

cac:AdditionalDocumentReference with an empty cbc:ID and a description, or a CII ram:AdditionalReferencedDocument without ram:IssuerAssignedID; in UBL a missing cbc:ID is already an XML schema error

Code Examples

Valid XML

<cac:AdditionalDocumentReference>
  <cbc:ID>TIMESHEET-2026-02</cbc:ID>
  <cbc:DocumentDescription>Timesheet February 2026</cbc:DocumentDescription>
</cac:AdditionalDocumentReference>

Invalid XML

<cac:AdditionalDocumentReference>
  <cbc:ID></cbc:ID>
  <cbc:DocumentDescription>Timesheet February 2026</cbc:DocumentDescription>
</cac:AdditionalDocumentReference>