Hi,
This happens due to Patch Level...
Check the patch level you may need to upgrade it ...
Alternative Approach (Even If Patch Level is not upgraded)
In IT 0009 you have "Purpose" option you can maintain "PRAN No." in that Field too... & finally configure payslip...
Go to PE 51 & enter Form Name ...finally select "Single Field" Option & create ...
Opt :-
Table :- XBT
Table Field:- ZWECK
Out Put Length:- 25
This will display PRAN No. in Pay slip..
Regards,
Veeram