BR-DEX-15

For invoices that declare themselves as an XRechnung extension (the $isExtension variable), the rule checks that the invoice does not contain any ram:ParentLineID element. The test is not(exists(//ram:ParentLineID)), so if any ram:ParentLineID appears anywhere, the rule reports a warning. ram:ParentLineID indicates use of sub invoice lines, which XRechnung does not support. Since severity is warning, the document is not rejected but the validator advises against this.

Remove all ram:ParentLineID elements from the invoice, or restructure the line items so no sub invoice lines are used.