What Is Peppol’s Five-Corner Model in E-Invoicing?

The Peppol five-corner model adds one more party to ordinary e-invoice exchange: the tax authority. A standard Peppol exchange runs on four corners — sender, sender’s service provider, receiver’s service provider, receiver. In the five-corner model, the service provider also reports the data from an issued or received invoice to the tax authority, in a separate document. In OpenPeppol’s Tax Data Document specification — the tax-data document being the machine-readable record the authority receives — the sender’s service provider creates a tax-data document alongside the invoice and sends it to the tax authority’s service provider, which passes it on to the authority. One thing to settle up front: as of July 2026, Peppol is not a general EU obligation. ViDA requires digital reporting and e-invoicing, but not Peppol specifically. Peppol is one way to meet it, not the only way.

The Four Corners Companies Already Use

Before the fifth corner makes sense, the four have to be clear — because that’s where almost all Peppol exchange happens today.

How the Four Corners Connect

OpenPeppol describes the four-corner model like this: the sender (C1) hands invoice data to its service provider (C2), which forwards the invoice to the receiver’s service provider (C3), and from there it reaches the receiver (C4).

What ties these parties together is the Peppol infrastructure itself. Each sender connects to one service provider and reaches every receiver on the “connect once, reach everyone” principle. Behind that sits a central addressing service — the Service Metadata Locator — which tells you which other service provider to contact, and a capability lookup, the SMP (Service Metadata Publisher), which shows what documents the receiver actually accepts. Every Access Point is Peppol-certified and bound by shared security rules.

Why the Tax Authority Never Sees the Invoice

In this model the tax authority never sees the invoice. The invoice moves between sender and receiver. That’s it.

The Fifth Corner Is the Tax-Reporting Corner

The fifth corner isn’t a new buyer or seller. It’s the tax authority’s side of the architecture. In OpenPeppol’s tax-data document model, C5 is the tax authority’s service provider — it receives the tax-data documents and forwards them to the tax authority itself (C6).

How the Reporting Flow Works

The process works like this. When the sender’s service provider (C2) sends an invoice, it also builds a tax-data document and reports the issued invoice to the tax authority through C5. The receiver’s service provider (C3) may, for its part, report receipt of the invoice down the same path. The invoice itself still travels from C1 to C4. Tax reporting runs alongside it, in parallel.

So the four-corner model doesn’t “switch over” into a five-corner one. The fifth corner is added next to ordinary invoice exchange when the law requires it.

What Actually Travels to the Fifth Corner?

This is where most of the confusion starts. The fifth corner doesn’t always get a copy of the invoice. OpenPeppol’s TDD specification splits the tax-data document into three parts: metadata (who is reporting, when, and in what role), an extract of data pulled from the invoice, and the option to include the entire invoice — either as an attachment or in extended form.

Why National Law Decides the Contents

Which of these actually moves depends on national law. The same specification says plainly that the document’s content, sequence and timing follow that country’s legislation and objectives. One country may ask only for an extract of the core data; another may want the whole invoice. There is no single tax-data package that applies to every country. Don’t assume there is one.

Why ViDA Made This Model Interesting Again

The five-corner model existed earlier, but ViDA — “VAT in the Digital Age” — put it back on the table. The ViDA package was adopted on 11 March 2025 and entered into force on 14 April 2025; from that point, member states may, under certain conditions, mandate e-invoicing.

The Two Dates That Matter

Digital reporting for cross-border B2B trade — the Digital Reporting Requirements, meaning near-real-time transaction data sent to tax authorities — start on 1 July 2030. Countries that already run domestic real-time, transaction-based reporting must align it with the EU model by 1 January 2035. This is exactly where the fifth corner comes in: it’s the technical way invoice data reaches the tax authority in real time.

Whether Peppol Will Be the Chosen Route

Whether Peppol will be that way hasn’t been decided. OpenPeppol launched the Peppol ViDA pilot to show whether Peppol formats built on the EN 16931 standard (the European e-invoice standard) and the Peppol network can meet ViDA’s expectations. Every EU tax authority has been invited to join. It’s a trial, not an obligation.

What This Means in Estonia and Latvia Right Now

You have to keep today’s obligation separate from tomorrow’s architecture.

Estonia: A Buyer-Triggered Right

In Estonia, an amendment to the Accounting Act that took effect on 1 July 2025 gives any company registered in the business register as an e-invoice recipient the right to demand an e-invoice from the seller. That’s a buyer-triggered right, not a general “Peppol only” B2B mandate. It doesn’t include fifth-corner tax reporting at all right now.

Latvia: A Staged Rollout

Latvia’s plan is more staged. According to Latvia’s VID description, e-invoicing is mandatory between the state and businesses (G2G, B2G, G2B) from 1 January 2025. Submitting the e-invoice data for those same segments to the VID became mandatory from 1 January 2026. In B2B — between businesses — payment documents must be issued as e-invoices, and issued e-invoices submitted to the VID, from 1 January 2028, while B2B data can be submitted voluntarily during 2026–2027. The e-invoice must reach the VID within five working days of being sent. Latvia’s national e-invoice format is XML and must comply with the Peppol BIS Billing 3.0 specification.

That’s already five-corner logic in practice, because the tax authority receives the invoice data — even though Latvia uses not only Peppol but also the national e-address and the VID’s own API.

The Five-Corner Model Is Not the Same as Clearance

This distinction matters. In a clearance model, the tax authority has to approve the invoice first, and only then does it reach the buyer. That’s how some Southern European and Latin American systems work.

The Peppol five-corner model works differently. The invoice moves from sender to receiver as usual, and the tax data goes to the tax authority in parallel — often later. It’s not the case that every invoice has to be approved in a tax authority portal before it can reach the buyer. In the five-corner model, it doesn’t work that way. Even in Latvia the data is submitted to the VID after the invoice is sent, not before.

What to Ask Your Service Provider

Before you start relying on Peppol for tax reporting, it’s worth checking a few things with your provider:

• Are you a certified Peppol Access Point? Without that, it isn’t the Peppol network, whatever the format.
• Which formats do you support? Specifically EN 16931, Peppol BIS Billing 3.0 and PINT (the Peppol International Invoice profile), which the ViDA pilot is built on.
• Are you ready for tax-data reporting? Can you create a tax-data document and send it via C5 if a country requires it.
• How do you handle country-specific rules? Latvia’s VID five-working-day rule and Estonia’s buyer-triggered e-invoice right are different, so one solution doesn’t automatically cover both.
• What’s the audit trail? Whether every sent invoice and every submitted tax-data document is traceable and retained.

There is no monetary threshold inside the Peppol five-corner architecture itself. Scope and thresholds always come from the legal obligation that uses the architecture. Peppol, EN 16931, ViDA digital reporting and national rules are four separate layers. Keep them apart, and you make the decisions at the right time, on the right basis.