service tax on forex transaction

Dear Members   Question :service tax on export Invoice (for service rendered ) $1000 provided in books (1000*44*10.30/100)=4532/-provided and paid in next month . now after four months amount realised  @ $ 47. now for differential amount (1000*3(47-44)*10.30/ 100) will service tax need to pay pl reply. I AM REFERING THE Provisional point of taxation wef 01.07.2011