What is the difference between UBL and XRechnung?
UBL 2.1 is an XML syntax. XRechnung is a German CIUS of EN 16931 and uses UBL or CII. Peppol BIS Billing 3.0 is a different CIUS of EN 16931 and uses UBL. This page creates UBL under Peppol BIS Billing 3.0; for German public authorities, use PDF to XRechnung.