Dear Vipin,
As you have mention that , you have maintained OKB9 on the Business area.
As per given notesystem does not determined Default cost object from OKB9 for automatically generated lines that reference the entire document and not individual items.
in this case you can apply the solution which is given to Note.this note can be used for all system generated line item.
Please confirm one thing At the time of posting which object you are using as mandatory like Business area , Business place.
Regards
Raheem