RFFOEXIT is the user exit for the payments medium program for HR Payment Salary. using this user exit you can modify bank format output.
Transaction in SAP HR such as PC00_M38_FFOT ( International Payment Medium ) – SWIFT Format MT100 is used for SAP HR to generate MT100 format for Bank. You can use User Exit RFFOEXIT to do that go to SE38 and open RFFOEXIT program.
In program RFFOEXIT you will found several sub routine that called user exit ( CALL CUSTOMER-FUNCTION nnn ) . you can specify which user exit that suitable for your country on the first ABAP Code in Comment. For International Payment you can create user exit 900.