e-invoicing strategy of the Belgian public sector

The continuous improvement in our standard of living, goes along with in an increase of commercial transactions. This is in turn causing an increase in the volumes of administrative documents, first of all invoices. In Belgium, one billion invoices are sent every year. Automated processing of these invoices would save the equivalent of 3.5 billion euros per year. This is a capital stake.

Such automation underlies machine-to-machine interaction, eliminating the human intervention (unless exception). Indeed, it is the main source of efficiencies (and reduction of the burden). Generalizing such a machine-to-machine pattern, will require an improvement of the IT products and service offerings. The current offering is designed for bilateral exchanges and within limited groups, but fails to offer an affordable solution to support e-invoicing generalization. The IT sector must adapt its offering to a model that handles the transmission of any kind of document from any sender to any receiver the same  way. This shift will drastically reduce the costs of transmission and enable generalization.

The present article explains the strategy of the Belgian Public sector in the domain of e-invoicing. It addresses the following key-aspects:

Business to Government (B2G) e-invoicing

The public sector (a) is composed of many diverse entities involved in all kind of activities, and (b) receives invoices from a very wide range of economic actors. Therefore the B2G e-invoicing scenario faces challenges that are very similar to the generalization of e-invoicing. Additionally, because it represents 16% of the GDP, the public sector (a) will derive significant savings from B2G e-invoicing and (b) represents a market justifying the efforts that the IT sector will have to do, to adapt the offering in the generalization of e-invoicing. Finally, as a regulating entity, the public sector has also a responsibility to make the change happen. Probably the universal postal system that we all know, would never have happened without intervention of the public sector.

In conclusion, the Government expects B2G e-invoicing to (a) roll out early and (b) be the driver for the larger generalization – once the necessary IT shift has happened. This explains the consistent strategy adopted by the European Commission and many national and local governments, including Belgium.


In 2014, based on the results of a successful but limited-scale B2G e-invoicing pilot phase, the Digital Transformation Office (DTO) of the FPS BOSA, which is responsible for studying the IT-aspects of the generalization of e-invoicing, found that the application of the PEPPOL framework would resolve most of the issues blocking the adoption of B2B and B2G e-invoicing. This framework identifies different kind of contributors to the e-invoicing generalization: correspondents, software editors, service providers and authorities. It brings these actors together in a community and contributes to organizing their respective roles. It also provides a set of specifications, based on mature technical solutions, that act as guidelines for the IT-players willing to safely engage in the IT shift mentioned above. PEPPOL identifies the need for a common transport infrastructure, that builds on existing service provider platforms and bridges their islands into one coherent super-network. PEPPOL also organizes the necessary cohabitation of multiple formats must cohabit: all formats are welcome (the transport infrastructure can handle them), however no trading party can refuse to handle at least one "common denominator format" - the "lingua franca", that people only need to use when there is no other common format available with their correspondent. Finally, PEPPOL comes with many other features whose description falls outside the scope of this article. For more information on the rollout of PEPPOL in Belgium and useful links to PEPPOL-related information, please visit the official page of the Belgian PEPPOL Authority.

Starting 01/01/2016 BOSA DTO is the PEPPOL Authority in Belgium. It takes the charge of rolling out this framework within his jurisdiction. Across Europe 11 PEPPOL authorities have already taken the same role. The constantly growing adoption of PEPPOL over time, creates the conditions for the e-postal infrastructure that is indispensable to the realization of our ambitions.


Mercurius is a key component of the program of the Belgian Public sector toward e-invoicing generalization. Where PEPPOL fixes the need for a universal e-postal infrastructure, Mercurius acts as a central "electronic mail-room" for all public sector entities, receiving the mail-in and dispatching it to the right department, and collecting the mail out to put it properly on the e-postal network. Thanks to its perfect alignment with the PEPPOL framework, every business that is able to e-invoice public authorities, will also be able to e-invoice any other (private) customer at no additional cost, once the framework becomes widely used.

Many private sector entities are ready to send e-invoices, and to adopt the PEPPOL framework. However, not all the 5.900 entities composing the public sector, can stick to one single schedule. To create a sufficient reach for the early adopters from the private sector, Mercurius can temporarily convert e-invoices into PDF invoices, for the public sector entities that are not ready yet. This strategy combines different advantages: it makes much stronger to motivate the private sector, and easier to communicate; it also creates time for the public sector to design and execute the right e-invoicing adoption project, at the right market conditions. This is a capital benefit of Mercurius for the generalization of e-invoicing in Belgium.

Mercurius comes with a portal, whose primary function is to allow everyone to monitor the transmission and processing of its e-invoices to all government bodies with 100% reliability. What is more, suppliers that do not yet have suitable IT equipment, are able to easily submit their invoices using a form on this portal - until they shift to e-invoicing. Finally, the Mercurius portal welcome page contains all kind of links to useful information about e-invoicing in Belgium, B2G and B2B. More information about the access to the Mercurius portal and the scenarios it supports, are available in a separate article (see later).

Typical flow of a B2G e-invoice

The following graphs display the flow of the invoice among the components:

Graphical representation of the B2G  flow and its components, compatible with an "any-to-any" exchange model 

High-level description of each step:

  1. The supplier sends his invoice to the customer, using the PEPPOL transport infrastructure.
  2. Mercurius receives the invoice (on behalf of the customer).
  3. Mercurius puts the invoice in the mail-inbox of the customer.
  4. At his own pace, the customer picks up his mail.
  5. The customer processes the invoice.
  6. The customer prepares a response to the invoice and gives it to Mercurius.
  7. Mercurius sends the response to the supplier.


The following article provides a more detailed description of each step (main flow, variants...): The life cycle of an e-invoice to the Belgian public sector.

Benefits for each group

Benefits for the private sector

The main benefit is that this solution can be reused as is for generalized B2B e-invoicing. There is no investment "only for B2G".

Other key benefits:

  • All enterprises can reach all public entities the same way. Currently over 200 public sector entities already participate, but in the longer term the whole public sector will be reachable (5900 entities).
  • The Mercurius Portal provides 100% transparency in the reception and processing of the supplier's e-Invoice. Both sender and receiver "see" the same information, using the same tools on the same platform.
  • In the longer term, the costs of the IT offering will decrease, and the performance will raise faster.
  • The supplier is paid faster thanks to the automation of the processing.

Benefits for the public sector

  • All public sector entities enjoy the services of the central e-mailroom, and thus of the team who owns and operates it. They don't have to talk to all the service providers of all their suppliers, or even share different models. They get better market conditions. They collaborate with civil servants in charge with Mercurius and receive specific support for the integration phase. There is also functional expertise.
  • Mercurius can also temporarily convert the incoming format into a format that better suits the public sector entity. It can be human readable for the entities not willing to delay the growing adoption in the Private sector, but who need more time to properly integrate their financial systems at fair market conditions.
  • The adoption of the European Norm will be considerably facilitated. Directive 2014/55/EU mandates that,  by 19/04/2019, all European public sector instances should accept e-invoices compliant with European Norm EN16931. Meeting this obligation involves adapting IT systems. This comes with many challenges. Mercurius will act as a pass through system for the instances that are sufficiently advanced to perform these changes, and as a buffer for the other ones, relieving them from the pressure caused by the complications, while helping to take best and fast advantage of the positive side of the obligation.

Benefits for the IT sector

  • as explained, the global adoption of B2G e-invoicing will create the conditions needed to setup solutions that really suit to the generalization of e-invoicing, applying models that escape from the limitations of closed networks and endless bilateral agreements. It will create a new business as such.
  • in the longer term, it will generate opportunities to integrate the invoice data with other types of data and processes. such kind of integration is not possible with paper based data exchange and processes. example: integration of the electricity or telephone traffic management with the invoice flow.
  • Mercurius was also designed to help the IT sector. It provides many tools that make the adoption of the PEPPOL model much easier, paving the way for B2B e-invoicing and e-procurement:
    • the Mercurius portal has a special access for Service providers, called the Mercurius Access Point role. It makes possible for the service providers to track and trace all the invoices that flow through their systems to Mercurius,and back.
    • a test environment is available, integrated with the test systems of the Public sector entities. It facilitates to the sector to perform all kinds of tests in the large scale, without having to invest in testing infrastructure. Among other things, it comes with a publicly available test message lookup tool, that considerably streamlines several phases of test activities.

Other key-articles

Following articles provide additional information about the different aspects of B2G e-invoicing, PEPPOL and Mercurius.

  • Mercurius for the private sector: describes the B2G e-invoicing flows from the private sector perspective. It describes the different options, provides legal, financial, functional and technical information to help the private sector adopt e-invoicing.
  • Mercurius for the public sector: provides similar information but from the public sector point of view. 
  • Mercurius portal help: consolidates information that is specific to the portal. is also the help section of the portal.