Registration under central excise and customs

Hi!,

I am trader in Jharkhand and registerd under sales tax in Jharkhand and having import licence  ,I frequently import some items and supply to our customers after paying customs duty  and adding over margin/profit .My turn over in financial yr 15-16 was 42 lacs.

Do i require to be get registerd under central excise ,if  there any exemption clause for small traders .

Thanks in advance