PEPPOL and Mercurius Platform in Belgium

PEPPOL and Mercurius Platform in Belgium

Structured e-invoicing will become mandatory for all B2B transactions in Belgium by 2026.  A business must use the PEPPOL network and the Mercurius platform to meet this requirement.

This guide will explain the role of each platform, how they work together, and how a business will start using them to stay compliant.

Platforms Used for E-Invoicing in Belgium

Belgium uses two key platforms to handle e-invoicing:

• PEPPOL – A secure international network used to send and receive structured invoices.
• Mercurius – The national platform that receives and routes invoices to Belgian public authorities.

PEPPOL: The Standard Network for E-Invoicing in Belgium

PEPPOL is the standardized European network used in Belgium to exchange structured e-invoices securely. Managed by BOSA DTO since 2016, it allows businesses to send invoices to any public or private entity through certified Access Points (Flick network), removing the need for custom system integrations.

Key Functions of PEPPOL

• Provides a secure transport network
  PEPPOL allows businesses to send and receive e-invoices through certified Access Points. This removes the need for custom integrations between different systems.
• Enforces use of a common invoice format
  All participants must accept the PEPPOL BIS format. This ensures standardization and allows structured invoicing across sectors and systems.
• Validates invoice structure before delivery
  Invoices must pass PEPPOL validation rules before reaching the receiver. This reduces errors and improves data quality.
• Supports use across borders and sectors, including worldwide
  The same setup can be used for invoicing both public and private entities in Belgium, across Europe, and in other PEPPOL-enabled countries around the world.

Benefits of Using PEPPOL

• Ensures full compliance with public sector rules
  PEPPOL is the only accepted channel for sending e-invoices to public entities in Belgium, ensuring that all technical and legal standards are met.
• Reduces manual work and invoice errors
  Structured formats and automatic validations reduce the risk of rejected invoices and cut down time spent on corrections.
• Simplifies cross-border invoicing
  Businesses can use the same Access Point and format to invoice customers in other PEPPOL-enabled countries without extra setup.
• Improves transparency and delivery tracking
  Senders can track the delivery and response status of each invoice through their Access Point or connected system.

Mercurius: The National Platform for E-Invoicing in Belgium

Mercurius is the national e-invoicing platform used by Belgian public authorities. It receives structured invoices sent via the PEPPOL network and routes them to the correct entity. If needed, it converts the invoice into a PDF and sends status updates confirming delivery or rejection.

Key Functions of Mercurius

• Acts as the central inbox for public entities
  Mercurius receives all incoming e-invoices on behalf of Belgian public authorities and places them in the correct in-tray.
• Connects with PEPPOL to receive validated files
  Mercurius works with the PEPPOL network to receive structured invoices that have already passed technical validation.
• Supports fallback delivery when needed
  If a public entity is not ready for structured invoices, Mercurius can convert the file to PDF and send it by email.
• Sends back structured responses to the sender
  Mercurius returns a status update (accepted or rejected) through the same route, helping suppliers track invoice delivery.

Benefits of Using Mercurius

• One central system for all public entities
  Suppliers can send e-invoices to any Belgian public authority through a single, consistent channel.
• Built-in delivery fallback option
  If a public entity cannot process structured files, Mercurius converts the invoice to PDF and delivers it by email.
• Automatic status updates on each invoice
  Suppliers receive feedback on whether an invoice was accepted or rejected, with clear reasons when available.
• No need to manage direct integrations
  Businesses do not need to set up separate links with each public entity — Mercurius handles routing and format checks.

How an E-Invoice Is Sent Using PEPPOL and Mercurius

• Step 1: Prepare the invoice in PEPPOL BIS format
  The supplier creates a structured invoice (or credit note) using UBL 2.1 syntax and includes all required fields, such as the purchase order number.
• Step 2: Send the invoice through an Access Point
  The supplier sends the invoice to their Access Point provider (such as Flick Network), which forwards it through the PEPPOL network.
• Step 3: Validate the invoice format
  PEPPOL checks the structure and content of the invoice using validation rules. If errors are found, the invoice is rejected before delivery.
• Step 4: Deliver to Mercurius
  If the invoice passes validation, it reaches the Mercurius platform. Mercurius identifies the correct public entity and places the invoice in its digital inbox.

• Step 5: Receive status update
  Mercurius sends a Message Level Response (MLR) back to the sender through the same channel. This confirms whether the invoice was accepted or rejected.

  How to Start E-Invoicing with PEPPOL and Mercurius in Belgium

• Step 1: Choose a certified Access Point
  A business must connect to the PEPPOL network through a certified Access Point (Flick network). The Access Point will take care of the secure delivery, routing, and validation of the e-invoice.
• Step 2: Prepare the invoice in PEPPOL BIS format
  Create an invoice using the PEPPOL BIS format with the UBL 2.1 syntax. Include all required fields such as the purchase order number.
• Step 3: Register to get a PEPPOL ID
  The Access Point provider will help register the business in the PEPPOL directory (SMP) and get a unique PEPPOL ID for sending or receiving documents.
• Step 4: Test the invoice to make sure it is valid
  Check if the invoice meets the format rules and includes all the required information. This helps prevent delivery issues and rejections.
• Step 5: Send the invoice through the Access Point
  After testing, the Access Point will send the invoice on the PEPPOL network. The invoice will reach Mercurius, which will deliver it to the correct public entity and send back a status response.

Conclusion

From 2026, the use of e-invoicing will become mandatory for B2B transactions in Belgium. A business must prepare by using the PEPPOL network and the Mercurius platform. PEPPOL will handle the secure delivery of a structured invoice through a certified Access Point (Flick network). Mercurius will receive the invoice and send it to the correct public authority. This process will help a business stay compliant, reduce errors, and improve the speed and quality of invoice exchange.