Service tax on receipt basis

Dear All,

One of my client has deposited ST on receipt basis in Fy 2008-9 to 2010-11.

Service recipient was not paying ST. Bill amount is 100 Rs + 10.3 ST =  Rs 110.3

Service Recipient paid Rs 100.

My client makes reverse calculation on Rs 100 and paid ST. But the assessing officer is of opinion that my client should have paid Rs 10.3 as ST as he has received full amount for Services provided. 

Anyone can tell any case to support that ST has to be paid by making reverse calculation.

Thanks in Advance