Service tax -computation for Advances-Project Billing IL

Dear All ,

We are using aIL with Oracle Projects , we have a important need to to compute the Taxes especially Swach Bharat Cess and Service Tax on the Invoice amount less advance paid.

So if the Invoice is of Rs1000 and we have received a 10% advance so the net  ST and SBC payable is on 900 , while the Project Invoice is generated for 1000 Rs.

At the point of Invoice generation it should compute as

Rs 90 instead of 100.

Any help on this would be great...

Regards,

Binoy