Resolution: No Action
I am not involved in TC 434 but have got this information
maybe it is already solved - and then sorry for this
From the European Norm:
In the CreditNote “Payment due date” is mapped to CreditNote/cbc:DueDate. As far as we can tell the field does not exist in the Credit note.
In the CreditNote “Project reference” is mapped to CreditNote/cac:ProjectReference/ cbc:ID. As far as we can tell the field does not exist in the Credit note