Sub invoice lines are data elements which provide more detailed information about the individual invoice lines they come under. This makes it possible to add several sub invoice lines below a single invoice line, for example to reflect contractual specifications. An example of the hierarchy of invoice lines and sub invoice lines is given below:

To include sub invoice lines, you must use the XRechnung extension. The extension has been valid since 1 January 2021 as version 2.0.0 of the XRechnung specification. For more information about the XRechnung extension, please see the website of the Coordination Office for IT Standards (KoSIT).