Belgium E-Invoicing After the Grace Period: What ERP Vendors Need to Know

Belgium's three-month tolerance period for B2B e-invoicing ended on March 31, 2026. Starting today — April 1 — the Belgian tax authority can impose administrative fines on businesses that fail to send or receive structured electronic invoices via the Peppol network.

If you build or maintain ERP software that serves Belgian businesses, this is the inflection point. Your clients can no longer point to "good faith efforts" as a defense. They need working Peppol connections, compliant EN 16931 output, and the ability to both send and receive structured invoices. If your system can't deliver that, you're exposing them to penalties.

Here's what changed, what the penalty regime looks like, and what you should be doing about it right now.

What the Grace Period Actually Was

Belgium's B2B e-invoicing mandate took effect on January 1, 2026. From that date, all VAT-registered businesses established in Belgium were required to issue and receive structured electronic invoices for domestic B2B transactions. PDF invoices sent by email stopped being compliant on day one.

The Royal Decree published ahead of the mandate included a three-month tolerance period (January 1 – March 31, 2026). During this window, the tax authority would not impose fines — but only for businesses that could demonstrate they had taken "reasonable and timely steps" toward compliance. This was not a blanket amnesty. Businesses that made no effort were technically non-compliant from January 1.

The tolerance period served two practical purposes: it gave smaller businesses time to onboard with a Peppol Access Point, and it allowed the Hermes platform's data archive to remain accessible for download through March 31.

Both of those windows are now closed.

What Changed on April 1, 2026

Three things happened simultaneously:

1. Penalties are now enforceable. The Belgian tax authority (FOD Financiën / SPF Finances) can issue administrative fines for non-compliance with the e-invoicing obligation. There is no further grace period announced.

2. The Hermes archive is gone. Belgium's legacy e-invoicing platform, Hermes, was decommissioned on December 31, 2025. The government kept the portal open for data download through March 31, 2026. That access has now ended. If your clients haven't downloaded their historical Hermes data, it may no longer be retrievable through official channels.

3. The "good faith" defense is significantly weaker. During Q1, businesses could argue they were mid-implementation. Three months in, that argument carries much less weight. The expectation is that compliant systems are operational.

Belgium's Penalty Structure

The fine structure is straightforward and escalating:

First offense: €1,500
Second offense: €3,000
Third and subsequent offenses: €5,000 each

There is a three-month interval between violations before the penalty escalates to the next tier. In practice, this means a business that remains non-compliant throughout Q2 2026 could face €1,500 in April, then €3,000 in July — and €5,000 for every subsequent three-month cycle after that.

Beyond the direct fines, non-compliance creates downstream problems: rejected invoices from compliant trading partners, delayed payments because the receiving system doesn't accept non-structured formats, and potential VAT recovery issues if invoice data doesn't meet the structured format requirements.

Technical Requirements: The Compliance Checklist

For ERP vendors, the requirements haven't changed since January — but the consequences of not meeting them have. Here's what your system needs to support:

Invoice Format

All B2B invoices must comply with EN 16931, the European semantic standard for electronic invoicing. In practice, this means outputting Peppol BIS Billing 3.0 UBL documents. Credit notes must follow the same standard.

PDF invoices — even if attached to an email with structured metadata — do not satisfy the mandate. The invoice must be machine-readable end to end.

Network Connectivity

Peppol is the default transmission network. Every Belgian VAT-registered business must be capable of sending and receiving invoices via Peppol, even if they also use alternative channels by mutual agreement.

This means your ERP system needs a connection to a certified Peppol Access Point. If your product doesn't natively connect to Peppol, you need to integrate with a service provider that does — and that integration needs to handle both outbound (sending) and inbound (receiving) flows.

Alternative Channels

Belgian law does permit e-invoice exchange outside of Peppol, but only if both parties explicitly agree and the format still complies with EN 16931 (or the CEN/TS 16931 technical specification). The critical constraint: even businesses using alternative channels must maintain the technical capability to use Peppol. You cannot opt out of Peppol readiness.

Peppol Registration

Each business needs a Peppol Participant ID linked to their Belgian enterprise number (KBO/BCE number). Your ERP system should make it straightforward for customers to register and manage their Peppol identity — either through your interface or via clear handoff to their Access Point provider.

Receiving Capability

This is the detail many vendors overlook. The mandate requires businesses to receive structured invoices, not just send them. Your system needs to be able to ingest incoming Peppol BIS 3.0 invoices, parse them, and integrate them into your client's accounts payable workflow. A Peppol endpoint that only sends is not compliant.

What ERP Vendors Should Do Right Now

If you haven't finished your Belgium integration, here's the priority list:

Immediate (This Week)

Audit your client base. How many of your Belgian customers are actually connected to Peppol and actively sending/receiving structured invoices? If you don't know the answer, that's the first problem to solve. Customers who went through Q1 without connecting are now exposed to fines.

Check receive-side capability. Sending is table stakes. Verify that your system correctly receives and processes inbound Peppol invoices. Test with real documents from multiple Access Points — not just your own test environment.

Communicate to clients. If any of your Belgian users are not yet compliant, they need to know that penalties are now active. Send them clear guidance on what to do and how your system supports them. Don't wait for them to find out the hard way.

Short Term (April–May 2026)

Validate EN 16931 conformance. Run your invoice output through a validation tool that checks against the full EN 16931 specification — not just Peppol BIS schematron rules. Belgian invoices have specific requirements around the enterprise number (KBO/BCE), VAT identification, and payment terms that need to be correctly mapped.

Build monitoring. Set up alerting for invoice delivery failures, validation errors, and Peppol connection issues. Your clients won't check; you need to surface problems proactively.

Prepare for the next phase. Belgium has announced that from January 1, 2028, businesses will need to report e-invoice data to the tax authority in near-real-time using a Peppol 5-corner model. This replaces the current annual customer listing (jaarlijkse klantenlisting). Start planning your architecture now — the 5-corner model requires a fundamentally different data flow than the current 4-corner exchange.

Ongoing

Monitor Peppol BIS updates. Peppol is converging European BIS 3.0 and international PINT into a unified BIS 4.0 standard during 2026. Belgium, as a Peppol-first country, will likely be an early adopter. Watch for migration timelines from OpenPeppol and the Belgian Peppol Authority.

The Bigger Picture: Why Belgium Matters for ERP Strategy

Belgium is one of the clearest Peppol-first mandates in Europe. Unlike France (which uses a platform-based model with certified intermediaries) or Germany (which layers XRechnung on top of Peppol for B2G and is adding B2B obligations), Belgium went straight to "everyone on Peppol, structured invoices only, no PDF fallback."

For ERP vendors, Belgium is a leading indicator. If your Peppol integration works cleanly here — both directions, EN 16931 compliant, with proper Belgian tax identifiers — you have a foundation that transfers to the Netherlands (already Peppol-heavy), Germany (expanding Peppol use), and eventually any EU market that adopts the Peppol network as its e-invoicing backbone.

The vendors who built solid Belgium support in Q1 2026 are already ahead. If you're still catching up, the penalty clock is now ticking.

How Invoice Navigator Helps

Invoice Navigator is a compliance safety layer for e-invoicing pipelines. We sit between your ERP system and the network, validating every invoice against EN 16931, Peppol BIS rules, and country-specific requirements before it goes out — and flagging issues on inbound documents before they hit your client's AP workflow.

For Belgium specifically, we validate:

EN 16931 semantic conformance
Peppol BIS 3.0 schematron rules
Belgian-specific business rules (KBO/BCE number format, VAT identification)
Credit note and self-billing compliance

One API call. No false confidence from partial checks.

Learn more about Peppol compliance →

Frequently Asked Questions

What happens if a Belgian business doesn't send e-invoices via Peppol after April 1, 2026?

Starting April 1, 2026, the Belgian tax authority can impose administrative fines for non-compliance. The first offense carries a €1,500 fine, the second offense €3,000, and subsequent offenses €5,000 each. Beyond fines, trading partners using compliant systems may reject non-structured invoices, causing payment delays.

Can Belgian businesses still use PDF invoices for B2B transactions?

No. Since January 1, 2026, PDF invoices are not compliant for domestic B2B transactions between Belgian VAT-registered businesses. All invoices must be structured electronic documents conforming to EN 16931, transmitted via the Peppol network or an agreed alternative channel that meets the same standard.

Is Peppol the only allowed e-invoicing network in Belgium?

Peppol is the default and mandatory network — every business must be capable of using it. However, two parties can agree to exchange invoices through an alternative platform, as long as the format complies with EN 16931 or CEN/TS 16931. Even when using alternatives, both parties must maintain Peppol capability.

What format do Belgian e-invoices need to use?

Belgian B2B e-invoices must conform to the EN 16931 European standard. In practice, this means Peppol BIS Billing 3.0 UBL format. The invoice must include the Belgian enterprise number (KBO/BCE), VAT identification number, and other mandatory fields specified in the Belgian implementation of the standard.

What happened to the Hermes platform?

Belgium's government-operated Hermes e-invoicing platform was fully decommissioned on December 31, 2025. The data archive remained accessible for download through March 31, 2026. As of April 1, 2026, the Hermes portal is no longer available. All e-invoicing must now go through the Peppol network or agreed alternative channels.

What should ERP vendors do if their Belgian clients are still not connected to Peppol?

Act immediately. With the grace period over, every day without a Peppol connection exposes your clients to penalties. Help them select and connect to a certified Peppol Access Point, register their Peppol Participant ID using their KBO/BCE number, and verify that both sending and receiving flows work with structured EN 16931 invoices. Prioritize receive-side capability — it's the most commonly overlooked requirement.