delay period how to calucalate

Interest is payable for the delayed period only. in this case it is the delay for the period from the due date to the realisation date by the department of the cheque thru which the payment has been made

In this case interest will be lavied @ 13%pa on 1000000 for two months and along with this interest the company has to pay additional interest @ 13 % pa on intesrest not paid from march to june 08. the department can not levy penalty for that since its non payment of interest and not Service tax. and service tax has been paid by company own action and not after scn by department.