# UBL-SR-56

> An Invoice shall contain maximum one Originator document reference identifier (BT-17).

Checked against Peppol BIS Billing 3.0 2026.5

Canonical: https://einvoicecheck.eu/rules/ubl-sr-56

## Official rule text

An Invoice shall contain maximum one Originator document reference identifier (BT-17).

## Why did my invoice fail UBL-SR-56?

The Originator document reference (BT-17) identifies the originating tender or lot the invoice relates to, carried as cac:OriginatorDocumentReference/cbc:ID. EN 16931 allows at most one such identifier per invoice, keeping the link back to a single originating procurement document unambiguous.

## Common causes

- More than one cac:OriginatorDocumentReference element is present.
- Both a tender ID and a lot ID were emitted as separate OriginatorDocumentReference blocks.
- A reference was duplicated when copying procurement metadata.

## How do I fix it?

```
Keep a single reference: <cac:OriginatorDocumentReference><cbc:ID>TENDER-2026-42</cbc:ID></cac:OriginatorDocumentReference>, removing any additional ones.
```