# PEPPOL-EN16931-R005

> VAT accounting currency code MUST be different from invoice currency code when provided.

Checked against Peppol BIS Billing 3.0 2026.5

Canonical: https://einvoicecheck.eu/rules/peppol-en16931-r005

## Official rule text

VAT accounting currency code MUST be different from invoice currency code when provided.

## Why did my invoice fail PEPPOL-EN16931-R005?

When a VAT accounting currency (BT-6) is supplied, it must differ from the invoice/document currency (BT-5). This rule exists because BT-6 only carries meaning when VAT is reported to the tax authority in a currency other than the invoice currency; if they were identical, the accounting-currency VAT amount (BT-111) would be redundant.

## Common causes

- TaxCurrencyCode was copied from DocumentCurrencyCode, so both hold the same value (e.g. both EUR).
- The invoice template always emits TaxCurrencyCode even for domestic single-currency invoices.
- A merge/mapping error set the accounting currency equal to the transaction currency.

## How do I fix it?

```
Either remove <cbc:TaxCurrencyCode> entirely for a single-currency invoice, or give it a genuinely different currency: <cbc:DocumentCurrencyCode>SEK</cbc:DocumentCurrencyCode> with <cbc:TaxCurrencyCode>EUR</cbc:TaxCurrencyCode>.
```