Hi Dharmin,
if you want to call this function for other koart values you have to pass I_GL_FAEDE parameter.Other than you will get error message.
CALL FUNCTION 'DETERMINE_DUE_DATE'
EXPORTING
i_faede = ls_faede_e
I_GL_FAEDE = 'X'
IMPORTING
e_faede = ls_faede_i
EXCEPTIONS
account_type_not_supported = 1
OTHERS = 2.
p_it_output-netdt = ls_faede_i-netdt.