BT-117
How should VAT in BT-117 be calculated on a summary invoice?
Short answer
BT-117 is the VAT amount for the relevant tax category in the tax breakdown. On a summary invoice, the calculation must comply with EN 16931, Peppol BIS and the VAT Act. If VAT calculated historically for separate supplies differs from a calculation based on the combined taxable amount, the document structure and rounding must be designed to pass business validation without distorting the tax.
BT-117
Amount of VAT
Tax for a specific category in summary.
Summary invoice
More deliveries
May create rounding differences.
Validation
Mathematics of the document
Checks relationships between rows and summary.
ERP
Consistent rules
The calculation must be explainable and repeatable.
Conclusion
BT-117 must reconcile with the tax breakdown and calculation rules; resolve rounding differences systematically rather than manually changing one isolated field.
Not legal advice.