Adjustment of Down payment in milestone billing

Query - A client has paid some amount as down payment to vendor. And the billing plan consists of milestone billing. The client wants to adjust fixed percentage of down payment in every invoice (depends upon the no. of milestones). Is it possible to make such settings in SAP system so that client does not have to calculate it on paper and pay to vendor?

Example- Suppose project is worth of 10,000,00. vendor has been paid 100,000 (not in SAP payment terms. It is a mutual agreement between client & vendor). Now in billing plan 5 milestones are included and each invoice will come up to 200,000. Now on bill verification, client wants to adjust this 100,000 in every invoice by deducting 20,000. In this way vendor will be paid only 180,000 instead of 200,000.

My question is that is it possible to make such kind of payment terms while making billing plans. Can we make such settings in SAP system.

Please clarify my doubt.

Edited by: Pallavi Choudhary on May 28, 2008 11:41 AM