Peppoli's 4-corner model means that an e-invoice travels between the seller and the buyer through four parties: C1 is the seller, C2 is the seller's chosen sender service provider, C3 is the buyer's chosen receiver service provider and C4 is the buyer himself. The typical journey of an invoice is C1 → C2 → C3 → C4, whereby C2 can convert the seller's invoice into a standard Peppoli e-invoice and C3 in turn can convert it into a format suitable for the buyer's system. It is not necessary to use the same operator or the same software, because each sender and each recipient only need to connect to one service provider, so that the rest of the network is available. In Estonia, the e-invoice requirement does not automatically mean Peppoli: the Ministry of Finance is based on the principle of format freedom and both the Estonian and European e-invoice standards are used.
Basic facts
| Fact | Value | Valid from | Source |
|---|---|---|---|
| Participants in the Four Corners Model | C1 seller, C2 seller service provider, C3 buyer service provider, C4 buyer | as of 2026-09 | peppol.org |
| One connection, the entire network | Each sender and each recipient only needs to connect to one Peppoli service provider („connect ONCE, reach ALL“) | as of 2026-09 | peppol.org |
| Amendment to § 7¹ of the Accounting Act | Entered into force on 1 July 2025; the e-invoice handler ID or other receiving channel of the e-invoice recipient will be entered in the commercial register | 01.07.2025 | riigiteataja.ee |
| Buyer's right to request an e-invoice in Estonia | All accounting entities that have registered as recipients of e-invoices in the e-business register (RPS § 7¹ (7)) have the right; approximately 18,000 registered entities | from 2025 | fin.ee |
| Obligation to accept e-invoices for the public sector in the EU | Article 7 of Directive 2014/55/EU obliges contracting authorities to accept and process e-invoices that comply with the European standard; Peppoli is not mentioned as the only channel | valid, as of 2026-09 | eur-lex.europa.eu |
| ViDA cross-border digital reporting | Member States to adopt measures by 30 June 2030, application from 1 July 2030; package adopted on 11/03/2025 | 01.07.2030 | eur-lex.europa.eu |
How does a 1,200-euro invoice get from the seller's software to the buyer's accounting?
Take a specific example. You submit an invoice to an Estonian client for 1,200 euros and the client is the recipient of the e-invoice in the commercial register.
- C1 (You): You create the invoice in your sales software and click „Send.“ The work ends here for you.
- C2 (Your operator): the sender's Access Point converts the invoice into a valid Peppol message and must validate it according to Peppol BIS requirements before sending, i.e. check that the props and structure meet the standard.
- Finding an address: C2 asks the central address service (Service Metadata Locator, SML) which capability register (Service Metadata Publisher, SMP) your customer's data is in, and reads from there which documents the customer can receive.
- C3 (customer operator): receives the invoice and formats it to be suitable for the client's accounting software.
- C4 (client): A purchase invoice for 1,200 euros appears in the customer's accounting in machine-readable format, without anyone typing the numbers by hand.
One important limitation: validation is technical. The sender's access point does not confirm that the invoice is commercially correct or that the customer agrees to pay. Any dispute over price or volume is still resolved between you and the customer.
Why isn't Peppol an invoice portal?
This is often confused. SML and SMP are for finding addresses and capabilities, something like an electronic address book. There is no common environment where the seller „uploads“ the invoice and the buyer „downloads“ it: the invoice moves directly between service providers. The end user does not have to be a member of OpenPeppol, but the receiving capability must be published online, otherwise no one from the sender will be able to find him.
Does the Estonian e-invoice requirement mean Peppoli?
No. In Estonia, a general obligation to submit an e-invoice if the buyer is a public sector institution was introduced in 2019. In 2025, this was replaced by with a buyer-choice model and expanded to the private sector: Any accounting entity that has registered as an e-invoice recipient in the e-business register may request an e-invoice (RPS § 7¹ (7)). Unless otherwise agreed, the seller must submit an e-invoice. Amendment to the Accounting Act entered into force on 1 July 2025 and the recipient's e-invoice handler identifier or other receiving channel is also entered in the register. The requirement therefore concerns the format and channel that the buyer has published. Peppol is one common method, not the only one resulting from the law.
Peppoli network, EN 16931 and ViDA are three different things
The most misunderstandings arise from lumping these three together.
The four corners of Peppoli are a transmission network and a set of agreements: who connects with whom, how the address is found, how the message arrives safely.
The European e-invoice standard (EN 16931) is an agreement on the content and structure of an invoice. Article 7 of Directive 2014/55/EU obliges contracting authorities receive and process e-invoices that comply with European standards in public procurement, but does not name Peppoli as the only mandatory transmission channel.
ViDA is a reform of VAT reporting. The package was adopted on 11 March 2025 and published in the Official Journal of the European Union on 25 March 2025; Member States must adopt the measures by 30 June 2030 and apply them from 1 July 2030 for digital reporting of cross-border transactions. This is about reporting, not the mandatory nature of Peppoli. None of these dates make the four corners model legally mandatory in itself or oblige all domestic B2B invoices to go through Peppoli.
In practice, this means two things. Today, what counts is what your customer has marked as the receiving channel in the commercial register. By 2030, it will also matter whether your cross-border sales data is available in a structured format. A machine-readable invoice already does this work for you.
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FAQ
What is the Peppoli Four Corners Model and who are its participants?
The Peppoli four-corner model describes the movement of an e-invoice from seller to buyer through four parties: C1 is the seller, C2 is the seller's Access Point, C3 is the buyer's Access Point, and C4 is the buyer himself. The model ensures interoperability, allowing parties to exchange invoices without using the same operator or accounting software.
Does the Estonian e-invoicing obligation require the use of the Peppol network?
No, the principle of format freedom applies in Estonia and Peppol is just one of many transmission channels. From 1 July 2025, the buyer can request a machine-readable e-invoice, but the seller will transmit it through the channel and handler that the buyer has registered in the commercial register.
What is the difference between the Peppoli network, the EN 16931 standard and the ViDA directive?
Peppol is a technical transmission network and set of rules for the secure delivery of documents, while EN 16931 defines the semantic data content and structure of an e-invoice. ViDA is the European Union's VAT reform that will introduce mandatory standardized digital reporting for cross-border transactions from 1 July 2030.