Since 1 January 2026, companies established in Belgium and registered for VAT must send and receive their B2B invoices in a structured electronic form, through the Peppol network by default, with a few exceptions such as certain VAT-exempt activities. The tolerance period closed on 31 March, and by the summer more than a million companies had registered, according to the Federal Public Service Finance. If you are reading this, you are probably one of them. So the question is no longer ‘do we need to register?’, but a less comfortable one: do your invoices actually leave your software in the right format, or does someone re-key them by hand into a second tool?
Registered does not mean integrated
For many companies, compliance took the simplest route: a subscription to an invoicing platform, or the module offered by their accountant. That is perfect when all your invoices are born in off-the-shelf accounting software. It is far less so when they are born elsewhere: in a custom-built ERP, a site management tool, a booking platform, a back office grown over the years. There, the invoice already exists, with its lines, its discounts, its customer references. And to send it through Peppol, someone copies it into a second tool. Double data entry is back, at the very moment the law was meant to make it disappear.
Re-keying has a cost nobody measures, and errors everybody ends up paying for. We saw it with a financial coach who spent more time typing than advising: the pattern is exactly the same here, with a legal obligation on top.
What Peppol really requires, technically
A Peppol invoice is not a PDF attached to an email: it is a structured data file, in the Peppol BIS Billing 3.0 format, built on the European standard EN 16931. Every piece of information has a defined place, from the VAT number to the breakdown of rates, so that the recipient’s software can process it with no human involved. A PDF sent by email no longer counts as an electronic invoice in the legal sense. In practice, your software needs to do three things:
- Produce a valid structured invoice, from the data it already holds
- Send it over the Peppol network, through a certified provider called an access point
- Receive your suppliers’ invoices, because the obligation works both ways: you can no longer refuse an electronic invoice
That third point is often forgotten. A company that has wired up sending but still processes incoming invoices by hand has only done half the job.
Three ways to connect in-house software
There is not one right answer but three, depending on your volume and your budget.
Exporting to a third-party tool. Your software generates a file, a person imports it into the invoicing platform, which sends it over Peppol. It is quick to set up and inexpensive, but the handling stays manual and every step is a chance for error. Acceptable for a few invoices a month, unsustainable beyond that.
Connecting to an access point through an API. Your software produces the invoice in the right format itself and hands it automatically to a Peppol access point, which takes care of delivery. Incoming invoices come back through the same channel and feed straight into your data. This is the option we recommend in the vast majority of cases: a targeted piece of development, a single source of truth, no more re-keying.
Becoming your own access point. It is technically possible, but it requires certification and continuous operation. Suited to very high volumes or to software vendors, it is almost never the right call for an SME.
The real work is not where you think
On a Peppol integration project, the sending itself is the easy part. The real work sits upstream, in your data. A customer with no company number on file, VAT rates hard-coded, incomplete billing addresses, units of measure made up on the fly: everything a PDF tolerated, a structured format rejects. The first step of a serious integration is therefore an inventory of what your software actually stores, before writing a single line of connection code. It is the same principle as when you move off Excel: the gain comes less from the tool than from the clean-up of the data it forces.
An invoice re-keyed by hand into a second tool is a legal obligation met on paper, and a guaranteed waste of time in practice.
What it costs, and what is coming in 2028
An API integration into existing software is usually measured in weeks rather than months, provided the data is sound. Waiting, on the other hand, has a price: in the summer of 2026, the tax administration was still favouring dialogue over fines, but the fines are set, 1,500 € for a first infringement, then 3,000 € and up to 5,000 € for repeat offences. On the incentive side, enhanced tax deductions are available until 2027 for small businesses investing in e-invoicing; your accountant will tell you which ones apply to you.
Above all, the work does not stop in 2026. From 1 January 2028, Belgium introduces e-reporting: the near real-time transmission of invoicing data to the tax administration. An integration patched together today will have to be redone by 2028. A clean one will only need to be extended.
E-invoicing is not an invoice problem, it is a data flow problem. If your business runs on software built for you, that software is what needs to speak Peppol, not your accountant on its behalf. This is exactly the kind of work we take on in product engineering: start from what exists, put the data back in order, connect it cleanly. If your invoices still take a detour through re-keying, tell us about your tool: we will tell you plainly what it would take for them to stop.