Diagnosis
Header partners cannot be entered at item level.
INCLUDE 'NA_NO_PROCESSING_1' OBJECT DOKU ID TX LANGUAGE EN

Procedure
Enter the function &V1& into the partnerfunction screen of the document header. It is then automaticallyadopted into the individual items.
Functions AA and AW are a special case, because they can never occur inthe item differently to how they appear in the header, even if this isset in Customizing.