# UBL-SR-35

> Referenced purchase order line identifier shall occur maximum once

Checked against Peppol BIS Billing 3.0 2026.5

Canonical: https://einvoicecheck.eu/rules/ubl-sr-35

## Official rule text

Referenced purchase order line identifier shall occur maximum once

## Why did my invoice fail UBL-SR-35?

An invoice line may reference the Referenced purchase order line identifier (BT-132), linking the line to a specific line of the buyer's order. EN 16931 allows at most one such reference per invoice line, so cac:OrderLineReference/cbc:LineID must not repeat within a single cac:InvoiceLine.

## Common causes

- Two cac:OrderLineReference blocks on one invoice line.
- cbc:LineID repeated inside a single cac:OrderLineReference.
- A line that fulfils several order lines is modelled with multiple order-line references instead of separate invoice lines.

## How do I fix it?

```
Keep one order-line reference per invoice line: <cac:OrderLineReference><cbc:LineID>5</cbc:LineID></cac:OrderLineReference>; split fulfilment across separate invoice lines if needed.
```