The Peppol Participant ID is used in the Peppol network to clearly identify participants. A distinction is made between the sender ID and the receiver ID. If you send invoices via Peppol, your Peppol Sender ID will generally be based on your Global Location Number (GLN) or VAT ID number.
Invoice recipients require a receiver ID. For all public sector organisations receiving invoices via the ZRE or OZG-RE, the Peppol receiver ID is composed of the buyer reference (Leitweg-ID) and the prefix 0204 (e.g. 0204:991-33333TEST-33). You will find more information here.