From Point-to-Point to 5-Corner: How e-Invoicing Networks Work

Q: What is point-to-point EDI and why was it the default for decades?

**Electronic Data Interchange (EDI)** has been the backbone of B2B document exchange since the late 1970s. In a point-to-point EDI setup, two trading partners agree on a message standard - typically EDIFACT in Europe or ANSI X12 in North America - and build a direct technical link between their systems. Data flows over dedicated channels such as AS2 connections or VPN tunnels, with each side mapping its internal fields to the agreed format. This model took hold first in industries with large, stable supply chains: retail, automotive, aerospace, and healthcare. When you ship thousands of pallets a week to the same handful of warehouses, the upfront cost of setting up a dedicated EDI link pays for itself quickly through reduced manual processing and fewer errors. The drawback becomes obvious when partner counts grow. Every new supplier or customer means another mapping project, another connection to test, and another set of agreements to maintain. For organisations with hundreds or thousands of trading partners, point-to-point EDI becomes an expensive web of bespoke integrations.

Q: What is the 2-corner model?

The **2-corner model** is the simplest architecture: the seller (corner 1) sends a document directly to the buyer (corner 2). There is no intermediary, no network operator, and no routing layer. Classic point-to-point EDI is a 2-corner model - the defining characteristic is that the communication channel is bilateral, built for one specific pair of partners. For a handful of high-volume relationships, 2-corner works well. It gives both sides full control over the data format, transport protocol, and security. But it does not scale: trading with 500 partners means 500 separate connections to configure, test, and monitor.

Q: What is the 3-corner model?

In the **3-corner model**, a single intermediary sits between the two trading partners. The buyer and seller both connect to this central party, which handles format translation, validation, and delivery. The intermediary can be a commercial **Value-Added Network (VAN)** or a government-operated platform. VANs have served the EDI world for decades. They are typically asymmetric: the buyer selects a VAN and requires its suppliers to connect to it. If you supply goods to five large retailers, each using a different VAN, you may end up with five separate onboarding processes. Government platforms work differently - [Italy's SDI](/country/IT) (Sistema di Interscambio) and [France's Chorus Pro](/country/FR) are examples where the state operates the central hub and all parties must route through it. The 3-corner model reduces the number of connections each party needs to maintain (one, instead of one per partner), but it introduces a single point of dependency. If the central platform goes down or changes its rules, every participant is affected. And in the VAN world, the buyer's choice of intermediary can impose costs and technical constraints on suppliers who have no say in the matter.

Q: What is the 4-corner model?

The **4-corner model** decentralises the intermediary layer. Instead of one central hub, there are many - called **Access Points (APs)** - and each trading partner chooses its own. Corner 1 (the sender) connects to corner 2 (the sender's AP). Corner 3 (the receiver's AP) delivers the document to corner 4 (the receiver). The two APs communicate over standardised protocols and use a shared discovery mechanism to find each other. [Peppol](/blog/what-is-peppol) is the best-known 4-corner network, with over 300 certified Access Points in 98 countries. The DBNAlliance in the United States follows a similar architecture. The principle is "connect once, reach all": once you are on the network through any certified AP, you can exchange documents with every other participant without building new connections. Dynamic discovery is what makes this work at scale. When a sender's AP needs to deliver an invoice, it queries the network's directory (in Peppol, the SML and SMP) to find the recipient's AP and the document types it supports. No pre-arrangement needed. This is a fundamental shift from the bilateral agreements that define 2-corner and 3-corner setups.

Q: What is the 5-corner model?

The **5-corner model** adds a tax authority as the fifth corner. In a 4-corner network, invoices flow between trading partners and the government has no real-time visibility. In a 5-corner setup, the Access Points report transaction data to the tax authority simultaneously - either by sending a copy of each invoice or by transmitting summary data in real time. This is the architecture behind **Continuous Transaction Controls (CTC)** and **clearance models**, where the tax authority validates or approves invoices before (clearance) or at the same time as (real-time reporting) they reach the buyer. The advantage for governments is obvious: instead of relying on periodic VAT returns and audits, they get a live feed of commercial transactions. [France's 2026 B2B e-invoicing mandate](/country/FR) is the most prominent example of a 5-corner CTC system. Authorised Partner Dematerialisation Platforms (PDPs) act as Access Points that exchange invoices between businesses while simultaneously reporting to the DGFiP. The model preserves the decentralised, market-driven AP ecosystem of the 4-corner world while giving the tax authority the data flow it needs - a balance that several other countries are now looking to replicate.

Q: How do classic EDI and open networks compare?

**Cost** is where the models diverge most. Traditional EDI has high setup costs (mapping, testing, partner onboarding) but low per-transaction costs at volume. Open networks like Peppol flip that: onboarding is lightweight, but per-transaction or subscription fees from Access Points add up at scale. **Scalability** favours open networks. Adding a partner on Peppol is a directory lookup, not a project. In classic EDI, every new partner means weeks of mapping and testing. **Security** is strong in both camps but achieved differently: EDI relies on private VPN and AS2 connections negotiated bilaterally, while Peppol uses a centralised PKI with AS4 encryption. Many organisations run a hybrid - EDI for long-standing high-volume partners, Peppol for everything else.

What is point-to-point EDI and why was it the default for decades?

Electronic Data Interchange (EDI) has been the backbone of B2B document exchange since the late 1970s. In a point-to-point EDI setup, two trading partners agree on a message standard - typically EDIFACT in Europe or ANSI X12 in North America - and build a direct technical link between their systems. Data flows over dedicated channels such as AS2 connections or VPN tunnels, with each side mapping its internal fields to the agreed format.

This model took hold first in industries with large, stable supply chains: retail, automotive, aerospace, and healthcare. When you ship thousands of pallets a week to the same handful of warehouses, the upfront cost of setting up a dedicated EDI link pays for itself quickly through reduced manual processing and fewer errors.

The drawback becomes obvious when partner counts grow. Every new supplier or customer means another mapping project, another connection to test, and another set of agreements to maintain. For organisations with hundreds or thousands of trading partners, point-to-point EDI becomes an expensive web of bespoke integrations.

What is the 2-corner model?

The 2-corner model is the simplest architecture: the seller (corner 1) sends a document directly to the buyer (corner 2). There is no intermediary, no network operator, and no routing layer. Classic point-to-point EDI is a 2-corner model - the defining characteristic is that the communication channel is bilateral, built for one specific pair of partners.

For a handful of high-volume relationships, 2-corner works well. It gives both sides full control over the data format, transport protocol, and security. But it does not scale: trading with 500 partners means 500 separate connections to configure, test, and monitor.

What is the 3-corner model?

In the 3-corner model, a single intermediary sits between the two trading partners. The buyer and seller both connect to this central party, which handles format translation, validation, and delivery. The intermediary can be a commercial Value-Added Network (VAN) or a government-operated platform.

VANs have served the EDI world for decades. They are typically asymmetric: the buyer selects a VAN and requires its suppliers to connect to it. If you supply goods to five large retailers, each using a different VAN, you may end up with five separate onboarding processes. Government platforms work differently - Italy's SDI (Sistema di Interscambio) and France's Chorus Pro are examples where the state operates the central hub and all parties must route through it.

The 3-corner model reduces the number of connections each party needs to maintain (one, instead of one per partner), but it introduces a single point of dependency. If the central platform goes down or changes its rules, every participant is affected. And in the VAN world, the buyer's choice of intermediary can impose costs and technical constraints on suppliers who have no say in the matter.

What is the 4-corner model?

Over 300 certified Access Points in 98 countries. Connect once, reach every participant on the network.

The 4-corner model decentralises the intermediary layer. Instead of one central hub, there are many - called Access Points (APs) - and each trading partner chooses its own. Corner 1 (the sender) connects to corner 2 (the sender's AP). Corner 3 (the receiver's AP) delivers the document to corner 4 (the receiver). The two APs communicate over standardised protocols and use a shared discovery mechanism to find each other.

Peppol is the best-known 4-corner network, with over 300 certified Access Points in 98 countries. The DBNAlliance in the United States follows a similar architecture. The principle is "connect once, reach all": once you are on the network through any certified AP, you can exchange documents with every other participant without building new connections.

Dynamic discovery is what makes this work at scale. When a sender's AP needs to deliver an invoice, it queries the network's directory (in Peppol, the SML and SMP) to find the recipient's AP and the document types it supports. No pre-arrangement needed. This is a fundamental shift from the bilateral agreements that define 2-corner and 3-corner setups.

What is the 5-corner model?

The 5-corner model gives governments real-time transaction visibility without replacing the decentralised Access Point ecosystem.

The 5-corner model adds a tax authority as the fifth corner. In a 4-corner network, invoices flow between trading partners and the government has no real-time visibility. In a 5-corner setup, the Access Points report transaction data to the tax authority simultaneously - either by sending a copy of each invoice or by transmitting summary data in real time.

This is the architecture behind Continuous Transaction Controls (CTC) and clearance models, where the tax authority validates or approves invoices before (clearance) or at the same time as (real-time reporting) they reach the buyer. The advantage for governments is obvious: instead of relying on periodic VAT returns and audits, they get a live feed of commercial transactions.

France's 2026 B2B e-invoicing mandate is the most prominent example of a 5-corner CTC system. Authorised Partner Dematerialisation Platforms (PDPs) act as Access Points that exchange invoices between businesses while simultaneously reporting to the DGFiP. The model preserves the decentralised, market-driven AP ecosystem of the 4-corner world while giving the tax authority the data flow it needs - a balance that several other countries are now looking to replicate.

How do classic EDI and open networks compare?

Cost is where the models diverge most. Traditional EDI has high setup costs (mapping, testing, partner onboarding) but low per-transaction costs at volume. Open networks like Peppol flip that: onboarding is lightweight, but per-transaction or subscription fees from Access Points add up at scale.

Scalability favours open networks. Adding a partner on Peppol is a directory lookup, not a project. In classic EDI, every new partner means weeks of mapping and testing. Security is strong in both camps but achieved differently: EDI relies on private VPN and AS2 connections negotiated bilaterally, while Peppol uses a centralised PKI with AS4 encryption. Many organisations run a hybrid - EDI for long-standing high-volume partners, Peppol for everything else.

Which approach suits your organisation?

The answer depends on three things: how many trading partners you have, how many invoices you exchange, and what the regulatory environment demands. If you have a small number of deep, high-volume bilateral relationships - say, an automotive supplier shipping to five OEMs - point-to-point EDI may still be the most efficient option.

If your partner base is growing, if you trade across borders, or if you operate in countries that mandate e-invoicing through a specific network, then a 4-corner or 5-corner model will save you from building and maintaining hundreds of individual connections. The trend is clearly towards network-based exchange, driven both by government mandates and by the sheer impracticality of scaling point-to-point.

Most organisations do not need to choose just one approach. A realistic setup might combine legacy EDI for established partners, Peppol for European public-sector and mandated B2B flows, and a direct API connection to a government clearance platform where required. The vendor directory and comparison tool can help you find providers that support the mix you need.