The Peppol network

Peppol (Pan-European Public Procurement OnLine) is an international network for exchanging structured business documents. It started as an EU pilot project in 2008 to make cross-border public procurement simpler. Today it is an open infrastructure used by more than 30 countries to send and receive electronic invoices, credit notes, orders, despatch advices and catalogues.

Two pieces make Peppol work. First, a set of standard document formats, the most important of which is Peppol BIS Billing 3.0 for invoices and credit notes. It is based on the European EN 16931 semantic standard and uses UBL 2.1 as its XML syntax. Second, a delivery network based on the four-corner model, with certified Access Points and a distributed discovery layer (SML/SMP) that lets any sender route a document to any recipient.

The result: any business connected to Peppol can exchange invoices with any other connected business, without bilateral agreements, custom mappings or VPN tunnels.

A Peppol document flows through four corners. The seller and buyer sit at corners 1 and 4. Their Access Points sit at corners 2 and 3 and do the technical work.

When the seller sends an invoice to corner 2, the Access Point needs to know where to deliver it. Peppol solves this with a two-tier DNS-based lookup.

Every participant on the Peppol network has a Peppol Participant Identifier, made of a four-digit scheme code and a value. Common schemes are 0208 (Belgian KBO/BCE enterprise number), 9925 (Belgian VAT), 0190 (Dutch OIN), 0184 (Danish CVR) and 0007 (Swedish organisationsnummer).

The sender Access Point hashes the participant identifier and queries the Service Metadata Locator (SML). The SML is a DNS-based directory that returns the URL of the Service Metadata Publisher (SMP) holding the recipient's metadata.

The sender then queries that SMP, which returns: the recipient Access Point's endpoint URL, the document types and processes the recipient supports, and the public certificate to use for signing the AS4 message. The sender Access Point now has everything it needs and transmits the document directly to the recipient endpoint.

For most users this happens entirely behind the scenes. You only need to know the recipient's participant identifier (often the VAT or company number) and the rest is handled by Access Points and the discovery layer.

Several countries are extending the Peppol network for tax purposes by adding a fifth corner: the tax authority. As an invoice flows from seller to buyer, a copy or a summary is also reported in real time to the national tax administration. The tax office no longer waits for a periodic VAT return: it sees every invoice as it happens.

Belgium will introduce the Peppol five-corner model on 1 January 2028 for tax e-reporting via FPS Finance. France is implementing a similar architecture through Plateformes de Dématérialisation Partenaires (PDPs) connected to a central public portal. The EU's VAT in the Digital Age (ViDA) reform will require near real-time digital reporting for cross-border B2B transactions across all member states by 2030.

This is the direction of travel for European e-invoicing. The four-corner network is the foundation. The fifth corner is layered on top without changing how invoices themselves are exchanged.

Peppol is governed by OpenPeppol AISBL, a non-profit international association based in Brussels. OpenPeppol owns the technical specifications (the BIS profiles, the AS4 transport profile, the SML/SMP architecture), runs the central SML, and certifies the National Peppol Authorities.

Each country with an active Peppol presence has its own Peppol Authority that operates the network within that jurisdiction and certifies local Access Points. Examples: FPS Policy and Support in Belgium, AgID in Italy, Digdir in Norway, the ATO in Australia, IMDA in Singapore.

Anybody can become a Peppol Service Provider by passing the certification process. The list of certified providers is public. As a buyer or seller, you do not deal with OpenPeppol directly: you contract with a certified Access Point (or use a software platform that includes one).

A Peppol BIS Billing 3.0 invoice is checked against two layers of schematron rules before it is accepted on the network: EN 16931 (CEN) business rules (the BR-* family, around 70 rules) and Peppol BIS rules (PEPPOL-EN16931-* and country-specific, another 240 rules). Most Access Points will reject a document that fails any fatal rule, so it pays to validate before you send.

You can run the same checks for free with this site. The full reference of all 311 EN 16931 and Peppol rules, with explanations and fixes, is at the validation rules reference.