CII-SR-191: Line discounts and charges must not carry their own VAT details

What it means

Each discount (BG-27) or charge (BG-28) on an invoice line is checked for a CategoryTradeTax element, a block with a VAT category and rate. In EN 16931 a line discount or charge takes the VAT category and rate of the line it belongs to (BT-151 and BT-152), so it has no VAT block of its own.

Why it matters

This is a warning, so the file is still accepted. VAT is worked out from the line's own category and rate, so a VAT block on the discount or charge changes nothing. If it shows a different rate from the line, it only makes the file harder to read.

How to fix it

Delete the CategoryTradeTax from the line's SpecifiedTradeAllowanceCharge in the XML. Then check the VAT category and rate on the line itself, because those decide the VAT. In invoicing software, the rate is set on the line or item, not on the discount.

The rule as published

CategoryTradeTax should not be present

Where this rule applies