Key takeaways
- B2G e-invoicing is the sending of structured invoices from a business to a public body.
- A Royal Decree of 9 March 2022 made it mandatory in stages for suppliers of the federal state, based on contract value.
- The format is Peppol BIS Billing 3.0 (EN 16931), sent over the Peppol network to the Mercurius platform.
- Contracts worth 3,000 euros or less excluding VAT are exempt from the obligation.
Selling to a Belgian administration no longer ends with a PDF attached to an email. Since 2022, invoicing a public body means sending a structured e-invoice: B2G e-invoicing. The origin is European: Directive 2014/55/EU of 16 April 2014 required public buyers to receive and process invoices compliant with the EN 16931 standard. Belgium transposed it, then reversed the logic: it is no longer only public bodies that must be able to receive, it is suppliers that must send in the right format.
This article explains what B2G invoicing is, who is affected and from when, which platform carries the invoice to the administration, and which format to use to stay compliant.
B2G e-invoicing, defined simply
B2G stands for business-to-government: a business (the supplier) invoices a public organisation (the contracting authority). B2G e-invoicing adds a constraint on form: the invoice is not a free document but a structured file, read and processed automatically by the public recipient's software.
The distinction from a PDF is the heart of the matter. A PDF is an image for the human eye; you have to re-key it to use it. A structured e-invoice is a standardised file that public accounting ingests without re-entry. It is that structured form, and only that form, that satisfies the obligation.
What Directive 2014/55/EU required of the public sector
Directive 2014/55/EU set a common baseline: every public buyer in the Union must be able to receive and process an e-invoice compliant with the European semantic model, the EN 16931 standard. The aim was to end the proliferation of national formats that made each cross-border contract costly to tool up for.
In Belgium, transposition rested on the public-procurement legislation and was then completed by a calendar specific to suppliers. The Regions had in fact moved ahead of the federal level, with Flanders requiring e-invoicing from its suppliers as early as 2017. The shift therefore predates the general B2B mandate; the public sector served as the starting ground.
The timeline of the obligation for suppliers
At federal level, a Royal Decree of 9 March 2022 phased in the obligation to issue a structured e-invoice based on the estimated contract value. Three stages followed one another, from the largest contract to the smallest.
- 1
Contracts of at least 215,000 euros
1 November 2022Suppliers of federal public bodies must send a structured e-invoice.
- 2
Contracts of at least 30,000 euros
1 May 2023The obligation extends to mid-value contracts.
- 3
Contracts under 30,000 euros
1 March 2024The obligation covers low-value contracts, above the exemption threshold. This final stage, first set for 1 November 2023, was postponed by a Royal Decree of 4 September 2023.
Since that last stage, the e-invoice has been the rule for the bulk of federal public contracts. The only remaining margin concerns very small amounts: contracts worth 3,000 euros or less (excluding VAT) stay exempt from the obligation, unless the contracting authority requires it anyway. In practice, if you regularly respond to public orders, you are affected.
Mercurius: the entry point for invoices to the public sector
A B2G invoice is not sent to an email address: it reaches Mercurius, the central platform through which Belgian public services, both federal and regional, receive and process their electronic invoices. Run within the Federal Public Service Policy and Support (BOSA), Mercurius acts as the mailroom of the public sector.
The key point for a supplier: Mercurius is connected to the Peppol network. You therefore do not need to connect to the platform directly. Your software sends the invoice through a Peppol access point, and the network routes it to Mercurius and on to the right recipient service. For businesses without connected software, a web portal also lets you submit an invoice manually.
What you need to invoice a public body
An active enterprise number
It identifies your business on Peppol through the Belgian 0208 scheme.
Software connected to a Peppol access point
It generates the invoice in the Peppol BIS format and sends it to Mercurius.
The recipient public service's identifier
Each administration has an address to which the invoice must be sent.
The contract or purchase-order reference
Contracting authorities often require a commitment reference to match and pay the invoice.
B2G and B2B: the same basis, two distinct obligations
Invoicing the public sector and the B2B mandate share the same technology: the EN 16931 standard, the Peppol BIS Billing 3.0 format and the Peppol network. But they are two distinct obligations, each with its own legal basis and its own calendar.
| B2G invoice (public sector) | B2B invoice (businesses) | |
|---|---|---|
| Based on EN 16931 / Peppol BIS | ||
| Travels over the Peppol network | ||
| Dedicated public platform (Mercurius) | ||
| Entry into force | In stages since 2022 | 1 January 2026 |
| Source of the obligation | Directive 2014/55/EU | Belgian VAT reform |
In practice, a business already compliant for its public-sector invoices holds most of the tooling for the B2B mandate of 1 January 2026: software that generates Peppol BIS and a connection to the network. It is the same plumbing, applied to another type of recipient.
Invoice the public sector without leaving your software
YouInv generates your invoices in the Peppol BIS format and sends them over the Peppol network, to Mercurius as well as to your private clients.
What this changes for your business
If you work with administrations, the question is no longer whether you must invoice electronically, but whether your tool does it correctly: produce a valid Peppol BIS file, address it to the right public service and route it over Peppol to Mercurius. The PDF attached to an email belongs to the past for contracts subject to the obligation.
The good news is that there is nothing public-sector-specific to master in the file itself: it is the same format as your B2B invoices. The only specific point is the routing to Mercurius and the references the contracting authority asks for. Compliant invoicing software absorbs that difference without you touching the XML.
Further reading
- Directive 2014/55/EU: e-invoicing in public procurement: the European text behind B2G.
- Peppol BIS Billing 3.0: what the format contains: the invoice profile the public sector expects.
- Peppol Belgium: the B2B mandate on 1 January 2026: the same logic extended to the private sector.
The reference source prevails: the European Commission's eInvoicing in Belgium page, which details the federal calendar and the role of Mercurius.
What is B2G e-invoicing?
B2G e-invoicing (business-to-government) is the sending of structured invoices from a business to a public body. In Belgium, these invoices follow the Peppol BIS format, based on the EN 16931 standard, and travel over the Peppol network to the public Mercurius platform.
Is e-invoicing mandatory for public contracts in Belgium?
Yes. A Royal Decree of 9 March 2022 made structured e-invoicing mandatory for suppliers of the federal public sector, in stages based on contract value. Since 1 March 2024 the obligation covers contracts below 30,000 euros; only contracts worth 3,000 euros or less excluding VAT are exempt.
What is the Mercurius platform?
Mercurius is the central platform through which Belgian public services, both federal and regional, receive their electronic invoices. It is connected to the Peppol network and acts as the mailroom for the public sector. A web portal also lets you submit an invoice manually.
Which format should you use to invoice a Belgian public body?
The expected format is Peppol BIS Billing 3.0, a usage specification of the European standard EN 16931 built on the UBL 2.1 syntax. It is the same technical basis as the B2B mandate, sent over the Peppol network.
Is a PDF sent by email enough to invoice the public sector?
No. A PDF is an image for the human eye, not a structured e-invoice. For public contracts subject to the mandate, the invoice must be a structured file in the Peppol BIS format, sent over Peppol to Mercurius, not a PDF attached to an email.
