Service Tax calculation when client don't pay the tax

Hi, 

Suppose i provide a service for10,000.

Then Service tax = 10000*10.3%=1030

So the total billed amount to be paid by the client should be10,000+ 1030= 11,030



But what if the client pays only 10,000. And not the tax amount. What should be the Service tax amount now. And how it is calculated.(let me know the formula).

Thanks.