CII-SR-493: The net line total may appear only once in the totals

What it means

In the block that holds the invoice totals (SpecifiedTradeSettlementHeaderMonetarySummation), the net line total (NetLineTotalAmount) may occur once at most. The rule only counts the element and does not look at the amount inside it. EN 16931 has no business term for this element.

Why it matters

Software that reads the file expects each total to appear once. With two copies it cannot tell which amount is meant, so the file is treated as malformed and the invoice is rejected. This is a fatal error, not a warning.

How to fix it

This is almost always a fault in the software that created the file, not something you typed. Create or export the invoice again, and if the error stays, send the file to your software supplier and quote this rule. If you edit the XML yourself, search for NetLineTotalAmount inside the totals block and keep one copy or delete them all. The totals that EN 16931 requires are held in other elements, so removing this one does not take them away.

The rule as published

NetLineTotalAmount shall occur at most once in SpecifiedTradeSettlementHeaderMonetarySummation.

Where this rule applies