See, there are two parts to this question. One is on the revenue recognition angle and the other is the excise duty liability.

As far as excise duty goes, the Central Excise Act 1944 read with the Rules clearly mention two things - Excise duty is attracted on manufacture, but the liability to pay the amount arises on removal from the factory. So only when you remove the goods from the factory, you are liable to pay excise duty. Let's say you agreed upon the sale today i.e 28.8.2011, but removed the goods only on 5.9.2011. Then excise duty liability is for the month of September and the payment has to be made by 5th / 6th of October.

From a revenue recognition persepctive, looks doubtful if you can recognise revenue. You will have to prove that there is transfer of risks and rewards, property of goods passes to buyer, recoverability and certainity of sale consideration as per AS-9. If the terms of agreement can prove that buyer takes the risks and rewards even without removal from factory, only then can u recognise revenue.