The totals

The totals of a Factur-X invoice are not a transcription of the PDF: they are fields checked against one another. An invoice can be perfectly readable and perfectly correct to the eye, and still fail because the totals block does not tell the same story as the lines.

The line total (BT-106). It carries only the net line amounts, rounded to two decimals. Document-level allowances and charges do not belong in it: they come in later.

The allowance and charge sums (BT-107 and BT-108). As soon as a document-level allowance appears, its sum becomes mandatory, and the equality with the sum of the allowances is checked to the cent, with no rounding tolerance. On the charge side, the sum in Factur-X also covers logistics service charges declared in their own block: an easy line to forget when a total is transcribed by hand.

The total excluding VAT (BT-109). It is the line total less the document-level allowance and plus the document-level charges. It must appear in the totals block: showing it on the PDF is not enough, because the check is on the data.

The total including VAT (BT-112). It is the total excluding VAT plus the VAT total. It is still required when the VAT is nil, and it then equals the total excluding VAT. That is the case which catches out exempt and reverse-charge invoices.

The amount due (BT-115). It is the total including VAT less any prepaid amounts and adjusted by the rounding amount. Two traps here. If nothing is left to pay, you write zero rather than removing the element. And if a prepayment was deducted from the amount due without being declared in its own field, the sum will not balance: the rule checks the equality exactly, an absent prepayment counting as zero.

This is why these errors mostly reach hand-made or spreadsheet-derived exports: the chain is coherent on paper and incomplete in the data. Drop your invoice into Pruvue and the report will tell you which equality does not hold, with the rule's official text. On VAT errors, which are a family of their own, see the most frequent VAT errors.