CII-SR-391: Leave the prepaid flag out of invoice discounts and charges

What it means

A discount (BG-20) or charge (BG-21) on the whole invoice contains a PrepaidIndicator element, a yes or no flag saying the amount was paid in advance. EN 16931 has no such flag on a discount or charge, so the element should not be there.

Why it matters

This is a warning, so the invoice is still accepted. But software that follows EN 16931 does not read the element, so the buyer never sees what it says. It is worth fixing if you meant to tell the buyer that something was already paid, or if the buyer's system is strict about extra elements.

How to fix it

Remove the PrepaidIndicator element from the discount or charge. It usually comes from the export settings of your invoicing software, so look for a profile or format choice such as Extended and switch to EN 16931 (or XRechnung, if your buyer asked for it). If part of the invoice has already been paid, enter it as the amount already paid (BT-113) in the invoice totals instead.

The rule as published

PrepaidIndicator should not be present

Where this rule applies