Special G/L Indicator F Is Not Defined for Down Payment

Dear All,

While creating down payment request (t.code f-47), I specified 'F' in Trg.sp.g/l ind check

box, the system thrown a message as, 'Special G/L indicator F is not defined for down payment' . And When I tried with "A" in stead of "F", I am able to create Down Payment Request.

My question is that when "F" is the indicator for Down Payment request, Why system is not accepting?

Thanks