# UBL-SR-21

> Payee legal registration identifier shall occur maximum once, if the Payee is different from the Seller

Checked against Peppol BIS Billing 3.0 2026.5

Canonical: https://einvoicecheck.eu/rules/ubl-sr-21

## Official rule text

Payee legal registration identifier shall occur maximum once, if the Payee is different from the Seller

## Why did my invoice fail UBL-SR-21?

The Payee legal registration identifier (BT-61), in cac:PayeeParty/cac:PartyLegalEntity/cbc:CompanyID, is the company registration number of a payee that differs from the seller and may appear at most once. EN 16931 allows a single legal registration id for the one payee.

## Common causes

- Multiple cac:PartyLegalEntity/CompanyID entries are written for the payee.
- The payee's registry number and VAT number are both placed in CompanyID.
- Merged source data duplicates the payee legal entity block.

## How do I fix it?

```
Provide one value: <cac:PayeeParty><cac:PartyLegalEntity><cbc:CompanyID schemeID="0198">DK98765432</cbc:CompanyID></cac:PartyLegalEntity></cac:PayeeParty> and remove duplicates.
```