# UBL-SR-17

> Buyer legal registration identifier shall occur maximum once

Checked against Peppol BIS Billing 3.0 2026.5

Canonical: https://einvoicecheck.eu/rules/ubl-sr-17

## Official rule text

Buyer legal registration identifier shall occur maximum once

## Why did my invoice fail UBL-SR-17?

The Buyer legal registration identifier (BT-47), carried in cac:AccountingCustomerParty/cac:Party/cac:PartyLegalEntity/cbc:CompanyID, may appear at most once. This is the company registration number that identifies the buyer as a legal entity, and EN 16931 allows only one such value.

## Common causes

- Multiple cac:PartyLegalEntity elements are generated for the buyer, each with its own CompanyID.
- The buyer's trade register number and VAT number are both mapped into CompanyID instead of using the VAT identifier field.
- A template repeats CompanyID for both a national and a local registry.

## How do I fix it?

```
Provide one entry only: <cac:PartyLegalEntity><cbc:CompanyID schemeID="0198">DK16356706</cbc:CompanyID></cac:PartyLegalEntity> and delete duplicate PartyLegalEntity/CompanyID occurrences.
```