I received an advance of rs 45000/- as advance on 21-3-2012 and i paid service tax on back calculation on it on 31-3-2012 then i provided service in may i.e my invoive was raised on 2-5-2012 on receipt on other remaing sum received i.s 1,55,000 @ 12.36 person now how much should be the Gross sales without service tax and how i must account for it