Five-Corner Model

The Peppol-based CTC topology adopted across the Gulf.

Definition

Corners 1–4 are sender, sender's Access Point/ASP, receiver's Access Point/ASP, and receiver. The fifth corner is the national tax authority, which receives invoice data from the service providers. This decentralised model — chosen by the UAE (FTA) and Oman (OTA) — forbids direct ERP-to-authority connections; all traffic flows through accredited providers.

Origin

Derived from OpenPeppol's four-corner network model; the "five-corner" / CTC extension is described in OpenPeppol and national specifications (e.g. UAE Ministry of Finance, Oman Tax Authority Fawtara programme).

Example in context

Seller → ASP1 → (Peppol) → ASP2 → Buyer, while ASP1 and ASP2 each report the invoice to the tax authority as the fifth corner.

Related terms

• PINT-AE — the UAE invoice format carried over this model.
• ASP — corners 2 and 3 in the topology.