OpenPeppol is a non-profit institution with annual membership fees.
It’s a EDI-network which forwards invoices but also orders, status messages and tenders.
The invoicing part, Peppol BIS Billing 3.0, based on UBL, is a subset of the attributes requested for in EN16931, comparable to the EN16931-Profile of ZUGFeRD/Factur-X, which is based on CII. PEPPOL uses the AS/4 protocol, while plain formats like Factur-X/ZUGFeRD or the XRechnung are protocol agnostic. AS/4 in turn is based on Standards like https and SOAP.
Since senders and recipients typically use service providers within the Peppol network it is a classic “Four-corner”-model.
Already the senders prevalidate their messages.
Service providers can have the roles Access Point Provider, Service Metadata Publisher and/or National Authorities (maximum 1 per country).
The german “National Authority” is Kosit. OpenPeppol has many customers in northern Europe, but in the meantime also expanded to Australia and Japan.
The software used on the servers is usually available as open-source.
Apart from XRechnung, german federal authorities and some states also accept Peppol-(X)Rechnungen,
but apart from B2G there is also a lot of B2B traffic on the Peppol Network.
Currently (September 2021) there are around 500 (488 on 2021-09-20) members from 38 countries.
Officially listed are e.g.