FB01 :

a) ''Post Document''

b) No doc type as SA automatically comes.

c) No automatic posting key population as 40

F-02

a) ''Enter GL account Posting''

b) Doc type = SA

c) Posting key = 40

Ofcourse these (b and c) can be over written and there by a) also.

Both call SAPMF05A program at the back end.