Hi Soman,
Maintaining master data ia always a onetime activity no need to maintain for each & every transaction, Maintaing chapterid & it's combination with material is very much necessary as the provisions under central excise law. So, based on the legal requirements for Indian senearios SAP has provided T.Code: J1ID as a separate transaction to mainatian all Excise master data.
You will mainatain excise indicator for plant and customer as one time activity no need to maintain for each & every transaction. Coming to excise rate it is use if you are using Formula based tax procedure not in Condition based.
Search in google regarding CIN, you will find so many documents.
Let me know if you have any doubts.
Regards,
S.Himavanth.