Peppol makes use of a subset of the UBL 2.1 specification. UBL is an open standard maintained by OASIS. The official website is https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=ubl. It offers downloads for for XML schema files and code lists for UBL 2.1 (ZIP) (56 MB).
e-Rechnung.gv.at supports the Peppol-UBL format not only when used via the Peppol eDelivery network but also when using the invoice upload or the web service delivery.
Details on the transmission via Peppol are described here.
Details on how to handle BBG specific fields are described here.
Invoices with UBL document type
Invoice can be delivered in version 2.1. Credit notes with UBL document type
CreditNote can also be deliver in version 2.1.
The special fields "order reference" and "supplier number" are mapped to specific fields in UBL. The first matching field that is non-empty will be used.
/Invoice/AccountingSupplierParty/CustomerAssignedAccountID- Attention: this is not a valid Peppol-Element anymore - just contained for backwards compatibility
/Invoice/AdditionalDocumentReference/Attachment/EmbeddedDocumentBinaryObject- is only evaluated, if the invoice is received via the Peppol eDelivery network. When using UBL on other channels, like upload or Webservice, the specific means to provide attachments must be used.