Mercurius — the Belgian federal B2G gateway

Mercurius is the national e-invoicing platform to Belgian public authorities, operated by BOSA. Mandatory for federal contracts above EUR 30,000 excl. VAT since April 2019, it switched to PEPPOL-BIS 3.0 in July 2020 and now plays the role of national B2G concentrator.

History: from paper to PEPPOL via BOSA

2010-2014 — Pre-figuration. Fedict (rebranded BOSA in 2017) launches a dematerialisation platform for federal public procurement. Proprietary EFFICY / Drupal format.
9 March 2017 — Transposition Royal Decree. Transposition of Directive 2014/55/EU on e-invoicing in public procurement. The federal State, public bodies and contracting authorities are required to accept and process electronic invoices compliant with EN 16931.
April 2018 — Mercurius v1 launch. Effective production. UBL 2.0 format mandatory for new orders. Not yet mandatory for suppliers.
1 April 2019 — Supplier obligation (first tier). Any supplier to the federal state for a contract > EUR 135,000 excl. VAT must issue a structured e-invoice via Mercurius.
1 April 2020 — Lowered to EUR 30,000 excl. VAT. Extension to 95% of contracts by value, 80% by volume according to the BOSA 2020 report.
1 July 2020 — PEPPOL-BIS 3.0 migration. Mercurius switches entirely to the PEPPOL network. The former Mercurius e-Invoicing portal becomes Mercurius Network, a central PEPPOL access point.
2022-2024 — Regional convergence. All regions (Brussels via Hermes, Wallonia via Walloon Mercurius, Flanders via Vlaanderen e-Procurement) migrate to the same PEPPOL-BIS 3.0 infrastructure.
2026 — National reference point. With the B2B generalisation of 1 January 2026, Mercurius becomes the free PEPPOL access point by default for Belgian SMEs without a private provider.

Mercurius Network architecture

text mercurius-network-flow.txt

┌──────────────┐    UBL Invoice    ┌───────────────────┐
│ Supplier     │ ────────────────> │ Sender PEPPOL AP  │
│ (VAT-reg.)   │                   │ (Belfius, Unifiedpost,│
│              │                   │  Combell, etc.)   │
└──────────────┘                   └─────────┬─────────┘
                                              │ AS4
                                              ▼
                                   ┌───────────────────┐
                                   │  Mercurius        │
                                   │  Network          │
                                   │  (BOSA central AP)│
                                   └─────────┬─────────┘
                                              │
                                ┌─────────────┴────────────┐
                                ▼                          ▼
                  ┌──────────────────────┐     ┌──────────────────────┐
                  │  SAP / Workflow      │     │  Hermes (Brussels)   │
                  │  contracting auth.   │     │  Walloon Mercurius   │
                  │  (federal entity)    │     │  (regions)           │
                  └──────────────────────┘     └──────────────────────┘

Since the July 2020 migration, Mercurius is a PEPPOL Access Point (AP) among others, but plays a special role as the gateway to all Belgian contracting authorities. Three technical layers:

Layer 1 — PEPPOL Access Point. Mercurius operates an OpenPEPPOL-certified AP compliant with eDelivery specifications (AS4 ENTSOG/CEF). Domain: mercurius.be.
Layer 2 — SMP (Service Metadata Publisher). Mercurius publishes, for each Belgian public entity, the associated PEPPOL endpoint. Each contracting authority is identified by its BCE/KBO number (Crossroads Bank for Enterprises) in the ICD 0208 format.
Layer 3 — Internal workflow. Conversion from UBL to internal formats (SAP IDoc, Workday, Oracle Financials), status tracking, integration with e-Procurement budgetary tools.

B2G submission flow

The nominal flow of a B2G invoice via Mercurius:

The supplier issues the invoice in UBL 2.1 PEPPOL-BIS Billing 3.0 format from their ERP or PEPPOL portal.
Their sender PEPPOL AP (e.g. Belfius, Unifiedpost, Cegeka) resolves the recipient AP via the Mercurius SMP.
The message is transmitted via AS4 (eDelivery CEF) to Mercurius Network. Reception is confirmed by an AS4 Receipt RFC 5024.
Mercurius validates the invoice (UBL XSD, EN 16931 Schematron and CIUS Belgium). If OK, status RECEIVED; otherwise REJECTED with an SVRL report.
Mercurius routes the document to the accounting system of the contracting authority (SAP, Oracle, IFB Federal Bookkeeping).
Subsequent statuses (ACCEPTED, PAID, DISPUTED) are returned according to the PEPPOL Billing profile.

PEPPOL and Hermes integration

Mercurius is interoperable with its regional counterparts by design, since all of them use PEPPOL:

Hermes Brussels — see the dedicated page. Talan operates this AP for the Brussels-Capital Region and its bodies (Bruxelles-Propreté, Actiris, STIB, etc.).
Walloon Mercurius — SPW Digital operates a regional AP for the Walloon ministries, Walloon municipalities and autonomous public bodies (Forem, AWEX, AVIQ).
Vlaanderen e-Procurement — the Flemish Region has its own MAGDA-Mercurius AP operated by Vlaamse overheid - Digitaal Vlaanderen.
OpenPEPPOL global: Mercurius is listed in the OpenPEPPOL.eu registry with the BE authority code. Any foreign PEPPOL AP can send an invoice to Mercurius (useful for non-Belgian EU suppliers).

xml mercurius-sbd-envelope.xml

<?xml version="1.0" encoding="UTF-8"?>
<StandardBusinessDocument xmlns="http://www.unece.org/cefact/namespaces/StandardBusinessDocumentHeader">
  <StandardBusinessDocumentHeader>
    <HeaderVersion>1.0</HeaderVersion>
    <Sender>
      <Identifier Authority="iso6523-actorid-upis">0208:0473495177</Identifier>
    </Sender>
    <Receiver>
      <Identifier Authority="iso6523-actorid-upis">0208:0316380841</Identifier>
    </Receiver>
    <DocumentIdentification>
      <Standard>urn:oasis:names:specification:ubl:schema:xsd:Invoice-2</Standard>
      <TypeVersion>2.1</TypeVersion>
      <InstanceIdentifier>INV-2026-FED-000412</InstanceIdentifier>
      <Type>Invoice</Type>
      <CreationDateAndTime>2026-05-19T09:30:00Z</CreationDateAndTime>
    </DocumentIdentification>
    <BusinessScope>
      <Scope>
        <Type>DOCUMENTID</Type>
        <InstanceIdentifier>urn:oasis:names:specification:ubl:schema:xsd:Invoice-2::Invoice##urn:cen.eu:en16931:2017#compliant#urn:fdc:peppol.eu:2017:poacc:billing:3.0::2.1</InstanceIdentifier>
      </Scope>
      <Scope>
        <Type>PROCESSID</Type>
        <InstanceIdentifier>urn:fdc:peppol.eu:2017:poacc:billing:01:1.0</InstanceIdentifier>
      </Scope>
    </BusinessScope>
  </StandardBusinessDocumentHeader>
</StandardBusinessDocument>

Scope and thresholds

In accordance with the Royal Decree of 9 March 2017 and the Act of 17 June 2016 on public procurement:

Entity type	Mandatory threshold	Since
Federal State and FPS	EUR 0 (any invoice)	1 April 2019
Federal autonomous bodies (NMBS, La Poste, Skeyes)	EUR 30,000 excl. VAT	1 April 2020
Regions (Brussels, Wallonia, Flanders)	EUR 30,000 excl. VAT	1 May 2019
Municipalities and provinces	EUR 30,000 excl. VAT	1 January 2020
CPAS/OCMW and chapter XII associations	EUR 30,000 excl. VAT	1 January 2024
Domestic B2B (post 1 Jan 2026)	Any operation	1 January 2026

Technical specifications

Format: UBL 2.1 Invoice, compliant with PEPPOL BIS Billing 3.0 (CustomizationID urn:cen.eu:en16931:2017#compliant#urn:fdc:peppol.eu:2017:poacc:billing:3.0)
Process: ProcessID urn:fdc:peppol.eu:2017:poacc:billing:01:1.0
Transport: AS4 — OASIS ebXML Messaging Services 3.0 + AS4 profile, compliant with CEF eDelivery
Sender/recipient identifier: ICD 0208:<BCE without dots or spaces, 10 characters>
Validation: UBL 2.1 XSD + PEPPOL BIS Billing 3.0 Schematron + CIUS Belgium (BE-* rules maintained by BOSA)
Limits: 80 MB max per message, 200 InvoiceLine default (1,000 on request), permitted attachment formats PDF/A-3, PNG, XLSX, CSV

Foundations

Standards

Flagship messages

Tools