# BR-AE-2 — Reverse charge (AE): VAT ids missing

> https://billhorse.com/en/rules/br-ae-2/

## What does this error mean?

Under reverse charge (category AE) EN 16931 requires the Seller VAT identifier (BT-31, or tax registration BT-32) and the Buyer VAT identifier (BT-48) — so it is clear who owes the tax.

## How to fix it

Add the Buyer VAT id (BT-48) and make sure the Seller carries BT-31 or BT-32.