# The five-corner model explained: will the UK use it? > A five-corner model adds the tax authority as a fifth corner that receives invoice data. The UK starts in 2029 with four corners and no real-time reporting. - Canonical URL: https://einvoices.uk/news/five-corner-model-uk - Published: 20 October 2026 (2026-10-20) - Last updated: 20 October 2026 (2026-10-20) (not updated since publication) - Author: Floris Lindenaar, Editor, e-invoicing expert (https://einvoices.uk/authors/floris-lindenaar) - Publisher: einvoices.uk (https://einvoices.uk) - Type: Explainer - Topics: Four-corner model, Peppol, HMRC, Technical - Language: en-GB (UK English); covers the United Kingdom ## Sources - [Promoting electronic invoicing across UK businesses and the public sector: consultation response](https://www.gov.uk/government/consultations/promoting-electronic-invoicing-across-uk-businesses-and-the-public-sector/outcome/promoting-electronic-invoicing-across-uk-businesses-and-the-public-sector-consultation-response) - [Peppol Continuous Transaction Controls Reference Document](https://peppol.org/wp-content/uploads/2023/02/Peppol-CTC-Reference-Document-v1.0.pdf) - [Peppol model for Tax Data Document](https://docs.peppol.eu/poac/om/om-tdd/bis/) - [Tax update 2026: simplification, modernisation and fairness summary](https://www.gov.uk/government/publications/summary-of-tax-update-2026-simplification-modernisation-and-fairness/tax-update-2026-simplification-modernisation-and-fairness-summary) --- A five-corner model is the familiar Peppol four-corner exchange **plus a fifth corner: the tax authority**. As an invoice passes between the supplier's and buyer's service providers, one or both providers also send the invoice data to a government platform. The UK is **not** using a five-corner model at launch in April 2029, but it is the obvious route if HMRC later wants invoice data. ## Four corners first In the [four-corner model](https://einvoices.uk/news/four-corner-model-explained): 1. **Corner 1:** the supplier creates the invoice in its software. 2. **Corner 2:** the supplier's [Access Point](https://einvoices.uk/glossary#access-point) validates and sends it over Peppol. 3. **Corner 3:** the buyer's Access Point receives it. 4. **Corner 4:** the buyer's software imports it. The government announced on 23 June 2026 that Peppol "will be the core interoperability network for e-invoicing in the UK", and the UK has chosen this decentralised approach. See [Four-corner model explained](https://einvoices.uk/news/four-corner-model-explained). ## Adding the fifth corner In OpenPeppol's design for continuous transaction controls (Peppol CTC), set out in its September 2021 reference document, the sender's provider (C2) validates the invoice "in real-time, ensuring compliance with local requirements", then reports "the complete business document or a tax subset thereof (Tax Data Document or TDD)" to a Corner 5 service provider designated by the tax authority. The reference document defines Corner 5 as "government-controlled infrastructure, which receives data from C2 and/or C3". It describes two variants: - **Simplex:** only the seller's provider reports. - **Duplex:** the buyer's provider also reports receipt. Peppol already publishes live Tax Data Document specifications. One example, for Oman, describes how an issuer's provider "creates and sends a TDD document, reporting the issued invoice" to the tax authority through its service provider. ## Four vs five corners | | Four-corner | Five-corner | |---|---|---| | Invoice exchange | Provider to provider over Peppol | The same | | Tax authority receives data | No | Yes, in real time or near real time | | What is reported | Nothing | Full invoice or a tax data subset | | Who reports | n/a | Service providers (corners 2 and/or 3) | | Effect on the business | Send and receive through your provider | Largely the same; provider handles reporting | | UK from April 2029 | **Yes** | **No** | ## Where the UK stands **Confirmed:** - Decentralised model; Peppol is the core network. - "The government will continue to explore the potential benefits of RTR but will not introduce it alongside the e-invoicing mandate in 2029." (Consultation response, 26 November 2025.) - Any future real-time reporting "will build on e-invoicing infrastructure". **Not confirmed:** - Whether a future UK reporting system would use the Peppol five-corner model, a different data feed, or anything at all. - Any timetable. The government said reporting would come, if at all, "once e-invoicing use was well established." The consultation response's own glossary describes the five-corner model as "one way to incorporate RTR into a decentralised e-invoicing model". Several multinational respondents recommended Peppol "on either a four-corner or five-corner model". So the five-corner model is clearly part of the government's thinking, but it has made no decision. ## Why it matters even without a decision Choosing a decentralised Peppol network now makes a five-corner extension technically straightforward later. OpenPeppol's reference document says: "From a Tax Subject perspective, there will be limited changes and deviations between the Peppol 4-corner and Peppol CTC 5-corner models". For UK businesses, that suggests two things: - **Little rework.** If HMRC later added a fifth corner, most of the effort would fall on Access Points, not on you. - **Data quality matters now.** Whatever you send over Peppol is exactly what would be reported. Errors in VAT codes or VAT numbers would become visible to HMRC. ## What about cross-border trade? The EU's VAT in the Digital Age (ViDA) package introduces digital reporting for intra-EU business supplies from 1 July 2030. OpenPeppol's CTC reference document also sets out a harmonised approach for cross-border trade. The UK is outside the EU, so ViDA's reporting does not apply to UK domestic invoices. Some EU countries' domestic systems use reporting too. See [UK businesses selling to EU customers](https://einvoices.uk/news/uk-businesses-selling-to-eu-e-invoicing). ## What to do now - Prepare for a four-corner exchange in 2029. Do not pay for "HMRC reporting" features nobody has specified. - Choose providers that can show they already operate where reporting exists, which suggests they could adapt. - Read [Will HMRC require real-time reporting?](https://einvoices.uk/news/real-time-reporting-uk) and the glossary entry for the [five-corner model](https://einvoices.uk/news/five-corner-model-uk). ## Frequently asked questions ### What is the five-corner model? It is the four-corner Peppol exchange (supplier, supplier's provider, buyer's provider, buyer) plus a fifth corner: the tax authority, which receives invoice data from the providers in real time or near real time. ### Will the UK use a five-corner model in 2029? No. The UK will start with a decentralised exchange over Peppol and has said real-time reporting will not be introduced alongside the 2029 mandate. ### Would a five-corner model change how I send invoices? Mostly not. Reporting would be handled by service providers. OpenPeppol says that from the taxpayer's perspective there are limited changes between the four-corner and five-corner models. --- How to cite: "The five-corner model explained: will the UK use it?", einvoices.uk, 20 October 2026, https://einvoices.uk/news/five-corner-model-uk einvoices.uk is an independent publication and is not affiliated with HMRC or the UK Government. Nothing here is tax advice; check the sources and official GOV.UK guidance before acting.