UBL-CR-479: Do not give a VAT amount per unit on an invoice-level discount or charge

What it means

The rule looks at the discounts (BG-20) and charges (BG-21) placed on the whole invoice, directly under the invoice or credit note. It warns when the cac:TaxCategory inside one of them has a cbc:PerUnitAmount, a fixed amount of tax for each unit. EN 16931 uses applicable percentage VAT rates (BT-96 for a discount, BT-103 for a charge), not a tax amount per unit.

Why it matters

EN 16931 does not use cbc:PerUnitAmount in the VAT category of document-level discounts (BG-20) or charges (BG-21).

How to fix it

Delete cbc:PerUnitAmount from the cac:TaxCategory inside each cac:AllowanceCharge directly under the Invoice or CreditNote element. Give the discount or charge a VAT category code and, where required, a VAT rate, and check that the VAT breakdown adds up. Check the corrected file again.

The rule as published

A UBL invoice should not include the AllowanceCharge TaxCategory PerUnitAmount

Where this rule applies