Our's is a Pvt. security providing Co., we have to raise arrear bills relating to the period April'08 to Aug'09 in the month of Sep'09, and the query is at what rate the service tax is to be charged on the arrears amount for the above said period. So,we want to clarify that the applicable rate of service tax is 10.30% for the entire arrear bill period (or) we have to charge 12.36% from Apr'08 to 23rd Feb'09 and 10.30% w.e.f 24th Feb'09 to Aug'09. Please guide me in solving this matter, with supporting statutory backup if possible.