4 e-invoice generator setups pass every validator yet bill the wrong amount

A test of 15,000 synthetic e-invoices from 12 open-source generators found that 4 configurations pass KoSIT (XRechnung 3.0.2), CEN EN 16931 and Peppol BIS 3.0.20, yet on 472 of 600 invoices the amount due (BT-115) differs from what the shop order charged. The cause is rounding when converting a tax-inclusive cart into EN 16931 net arithmetic. A fix for Mustang is merged (PR #1318) but unreleased.

• 4 configurations mismatch the amount on 472 of 600 invoices
• Validators only check that an invoice is consistent with itself
• Mustang 2.26.0 and speedata/einvoice 0.0.23 are equally affected
• All 30 French Factur-X scenarios passed validation