5-Corner Model in PEPPOL: How Belgium Transforms E-Invoicing into E-Reporting Mandate

As of January 2026, Belgium’s e-invoicing mandate requires all VAT-registered businesses to issue and receive B2B invoices in a structured, machine-readable format using the PEPPOL network. Currently, this operates on the classic 4-corner PEPPOL model, where invoices are exchanged between the sender and receiver through their respective certified Access Points (APs), without direct involvement from government authorities. 

However, Belgium has already announced plans to move beyond e-invoicing to a full e-reporting mandate, expected to be implemented by 2028. This next step will introduce the 5-corner PEPPOL model, where tax authorities become an active participant in the invoicing process. Under this framework, every invoice will be automatically reported in real time to the Belgian tax authority as a fifth “corner,” enabling continuous transaction controls (CTC). The government will not only validate and clear invoice data before it reaches the buyer but will also have a central role in storage and audit, effectively integrating compliance checks into the flow. 

Belgium e-Invoicing Mandate and PEPPOL

Starting January 2026, all VAT-registered companies must issue and accept invoices in a structured, electronic format rather than traditional paper or PDF documents. The government has chosen the PEPPOL (Pan-European Public Procurement Online) network as the backbone for this transformation, mandating the use of the PEPPOL BIS Billing 3.0 (Universal Business Language XML) standard. 

The PEPPOL framework allows any company to use its preferred invoicing software, provided it connects through a certified PEPPOL Access Point, offering flexibility and interoperability. The mandate aims to reduce manual data entry, minimize errors, and enable faster, more secure exchange of invoices. 

PEPPOL and e-Invoicing Models

The PEPPOL network is an international framework that enables businesses and public entities to exchange electronic documents, like e-invoices, securely and efficiently, regardless of their internal systems or service providers. To achieve this interoperability, PEPPOL supports several “corner models” that define how invoices travel across the network, evolving to meet the needs of businesses and regulators.

E-invoicing models describe how electronic invoices are exchanged between businesses, and the “number of corners” refers to the key parties in the process. 

• The three-corner model involves the sender, receiver, and a shared service provider. This setup is suitable for closed networks but limited in flexibility. 
• The four-corner model became the standard in Europe. Here, the sender and receiver each choose their own Access Point, allowing for open, interoperable exchanges across any provider on the PEPPOL network.  
• Now, as governments pursue real-time tax compliance, the five-corner model is emerging, adding the tax authority as a direct participant. This model is essential when continuous transaction controls or e-reporting are mandated, enabling instant validation and audit. 

What is the 5-Corner Model in PEPPOL?

At its core, the 5-corner model is a digital ecosystem for structured e-invoice exchange, where each participant has a specific compliance and operational role. The flow is designed for maximum transparency, automation, and oversight.

The 5 participants in the PEPPOL 5-Corner Model:

This architecture supports seamless e-invoicing and tax data flows, especially as Belgium prepares for mandatory e-reporting (expected by 2028).

Why Belgium is Adopting the 5-Corner Model

Moving to a 5-corner model is not just a technical upgrade—it reflects regulatory strategy and futureproofs Belgian businesses.

• Regulatory Compliance: Anticipates EU VAT in the Digital Age (ViDA) requirements for e-reporting and cross-border transactions.
• Tax Integrity: Enables direct, real-time invoice data access for tax authorities, reducing VAT fraud.
• Seamless Interoperability: Preserves the flexibility and provider choice of the 4-corner model while adding automated tax controls.

5-Corner Model: Step-by-Step Process Flow

The 5-corner PEPPOL model is designed to integrate tax oversight seamlessly into the e-invoicing lifecycle, setting a new standard for compliance, automation, and auditability in Belgium’s upcoming e-reporting regime.

1. Invoice Generation & Standardization: The process begins with the supplier (Corner 1) creating a structured e-invoice using the PEPPOL BIS (UBL XML) format in their ERP or accounting platform. 
2. Transmission to Sender’s Access Point: Once generated, the invoice is transmitted to the supplier’s chosen PEPPOL Access Point (Corner 2). Here, the invoice undergoes automated checks for format integrity, business rule validation, and PEPPOL compliance. 
3. Real-Time E-Reporting to Government (Corner 5): A core innovation: the Access Point sends the invoice data in real time to the Belgian tax authority (FPS Finance) as part of Continuous Transaction Controls (CTC). 
4. Routing via the PEPPOL Network: After validation and reporting, the invoice is routed through the secure PEPPOL network to the recipient’s Access Point (Corner 3), using standardized addressing via the SMP directory.
5. Delivery to Recipient’s System: The recipient’s Access Point verifies the document and delivers it to the buyer’s ERP/accounting system (Corner 4), where it’s ready for automated booking, approval, and payment.
6. Acknowledgement and Audit Trail: Throughout the process, every transaction and status update is logged and acknowledged, creating a robust, time-stamped audit trail. 

Key Benefits of the 5-Corner Model for Belgian Businesses

As Belgium readies for e-reporting, these benefits are 

1. Real-Time VAT Oversight:  Continuous Transaction Controls mean every invoice can be checked by the tax authority before, during, or immediately after exchange, reducing the VAT gap and fraud.

2. True End-to-End Automation: With business and government in the loop, invoicing, compliance, and reporting are fully automated, minimizing manual intervention and risk.

3. Universal Interoperability: PEPPOL’s international standards (PEPPOL BIS 3.0 / EN 16931) mean invoices flow smoothly across borders.

4. Audit Readiness & Data Integrity: Time-stamped, validated records at every step make audits efficient and transparent. Data is structured, archived, and easily accessible for both businesses and authorities.

4-Corner to 5-Corner e-Invoicing Model: What Changes?

The traditional 4-corner model (Sender, Sender’s AP, Receiver’s AP, Receiver) is decentralized and provider-agnostic. The 5-corner model builds on this with these critical enhancements:

Implementing the PEPPOL 5-Corner Model in Belgium

Transitioning to this new model requires strategic upgrades:

• Adopt Compliant Invoicing Software: Ensure your solution exports invoices in PEPPOL BIS (UBL XML) format.
• Connect to a Certified Access Point: Partner with a PEPPOL-accredited AP for both sending and receiving invoices.
• Prepare for E-Reporting Integration:  Select software/APs that support integration with government e-reporting endpoints.
• Update Master Data: Maintain correct VAT numbers, PEPPOL IDs, and customer/vendor metadata.
• Test and Validate: Run pilot exchanges and CTC-ready invoice tests with partners and your AP.
• Plan for Data Security & Archiving: Digital archiving of e-invoices is mandatory, ensure your systems comply with Belgian/EU retention laws.

Conclusion

The 5-corner PEPPOL model preserves the flexibility and international interoperability of the original framework, allowing businesses of all sizes to connect via certified access points and exchange invoices using standardized formats such as PEPPOL BIS UBL. With real-time government oversight, every transaction is securely logged, validated, and archived, creating a seamless and fully automated flow of financial data. The system ensures audit readiness, reduces manual processing, and supports cross-border trade by aligning with European Union standards for digital invoicing and tax reporting.

To comply and benefit from the new model, Belgian companies need to update their invoicing systems, connect to certified PEPPOL access points, and prepare for integration with government e-reporting endpoints.