# UBL-SR-42

> Party tax scheme shall occur maximum twice in accounting supplier party

Checked against Peppol BIS Billing 3.0 2026.5

Canonical: https://einvoicecheck.eu/rules/ubl-sr-42

## Official rule text

Party tax scheme shall occur maximum twice in accounting supplier party

## Why did my invoice fail UBL-SR-42?

The Seller VAT identifier (BT-31) and the Seller tax registration identifier (BT-32) are each modelled as a cac:PartyTaxScheme under the accounting supplier party — one for the VAT scheme and one for other tax registrations (e.g. FC). EN 16931 therefore allows cac:PartyTaxScheme to occur at most twice for the seller; a third occurrence indicates an invalid or duplicated tax registration.

## Common causes

- A third cac:PartyTaxScheme added to the seller party.
- The same VAT registration repeated as an extra PartyTaxScheme.
- Multiple non-VAT tax registrations each given their own PartyTaxScheme beyond the allowed two.

## How do I fix it?

```
Limit the seller to two: one with cac:TaxScheme/cbc:ID = VAT (BT-31) and at most one other (e.g. FC for BT-32); remove any additional cac:PartyTaxScheme.
```