Belgium’s B2B e-invoicing mandate (1 January 2026), explained

As of 1 January 2026, Belgium requires structured electronic invoices between most VAT-registered businesses established in Belgium (B2B). A PDF attached to an email no longer counts: the invoice has to be a machine-readable document conforming to the European standard EN 16931, exchanged in the Peppol BIS format over the Peppol network by default. The goal is the same as the French and German mandates — a structured, automatable invoice — reached through Belgium’s own Peppol-first route.

What the mandate requires

For in-scope B2B transactions, the supplier must issue a structured electronic invoice and the customer must be able to receive one. “Structured” means the invoice data lives in a defined XML model — not pixels in a PDF and not a flat image. In practice that means an invoice built to the EN 16931 core data model, carried in the Peppol BIS Billing profile, and sent through a Peppol access point rather than by email. Both sending and receiving capability are part of the obligation.

Who is in scope

The mandate targets VAT-registered businesses established in Belgium invoicing each other (B2B). Belgian law sets specific exclusions — for example certain taxpayers in bankruptcy, some flat-rate regimes, and parties without the required Belgian establishment can fall outside the obligation, and B2C and certain cross-border flows are treated differently. Because the boundaries are defined in law and updated by the authority, treat the list above as orientation, not a determination: check your specific situation with FPS Finance or your accountant.

The format: Peppol BIS on top of EN 16931

Belgium’s default is Peppol BIS Billing. Peppol BIS is a CIUS — a Core Invoice Usage Specification — layered on top of EN 16931: it takes the European core invoice model and adds its own rules and code-list constraints, and it uses the UBL syntax. So a Peppol-compliant invoice is always EN 16931 core compliant, but the reverse is not automatic — Peppol BIS asks for more than the core alone. See what EN 16931 is for the core model and the UBL vs CII distinction.

How Peppol transmission works (the four-corner model)

Peppol is a network, not a file format. In its four-corner model the sender (corner 1) hands the invoice to its access point (corner 2), which routes it across the Peppol network to the receiver’s access point (corner 3), which delivers it to the receiver (corner 4). Participants are addressed in a shared directory. Getting onto the network requires a certified Peppol access point — that is the piece that physically sends and receives the document. Producing a correct invoice file and getting it onto Peppol are two separate jobs.

Where Slipstack fits — and where it does not

Slipstack is on the document side of that split, not the network side. From one JSON call it can:

• Generate an EN 16931 core invoice in UBL or CII syntax, or a Factur-X / ZUGFeRD PDF with the XML embedded.
• Validate the EN 16931 core business rules for free before you send anything, with the EN 16931 / XRechnung core validator.

What Slipstack does not do: it is not a Peppol access point, it does not transmit invoices, and it does not register you on the network. It also covers the EN 16931 core, not the additional Peppol BIS CIUS rules — so a core-valid invoice from Slipstack is a correct starting point, but your access point or service provider is responsible for Peppol BIS conformance and delivery. For what a mandated routing platform is, see what is a PDP.

Related: France mandate · Germany mandate · EN 16931 explained · Factur-X / ZUGFeRD · What is a PDP.