Required format
Belgium mandates the Peppol BIS Billing 3.0 format (UBL 2.1 syntax), fully compliant with the European standard EN 16931. Belgium does not apply any national variations to the standard.
An alternative format may be used only by mutual written agreement between both trading parties. However, every taxpayer must always be technically capable of issuing and receiving Peppol BIS invoices regardless of any such agreement.
Rounding rules (from 1 January 2026)
From 1 January 2026, rounding is only allowed on the total VAT amount per rate - not on individual line items. This aligns with the structured format requirements.
What this means in practice: If an invoice has 10 line items all subject to 21% VAT, the VAT is calculated and rounded once on the combined total - not separately on each line.
Sources: Peppol BIS Billing 3.0 documentation; Royal Decree on Structured Electronic Invoices (Art. 54 Belgian VAT Code)
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