Peppol is an interoperability framework and network for exchanging structured business documents, such as e-invoices, between organisations that use different software. It is run by OpenPeppol, a non-profit international association under Belgian law. It works on a four-corner model: sender and receiver each connect to a Peppol-certified service provider called an Access Point, and Access Points find each other through the network's lookup services (SML and SMP). Its invoice specification, Peppol BIS Billing 3.0, covers invoices and credit notes in UBL syntax, with element names taken from the European standard EN 16931. You meet it when a customer asks to receive invoices “via Peppol” rather than by email. Example: a supplier's accounting software passes a BIS Billing invoice to its Access Point, which delivers it to the buyer's Access Point and into the buyer's system. Common mistakes: calling an emailed PDF or XML file “sent via Peppol” when it never went through an Access Point, and assuming any EN 16931 file is Peppol-ready. Invoice Forever's EN 16931 export, for example, carries no Peppol participant ID.
Try it: E-invoicing by country.