Service tax related query

In an entry, if output is completely offsetted by input, why would there be any balance left to be carried to P&L, If you say that output is not offsetted by year end, then the argument is not accepted because for year end i.e. 31st March the output should be offsetted by input.

Now, if there is any balance left, then sales tax paid is not our expense, rather collected from customers and then deposited to govt. Therefore it can never show in P&L. Interest or Penalty paid on above can be shown in P&L expense side.

Dear Sir,

We have a company got a contract for setting up factory. We have given sub-contract to one individual. Under composit shcmen, we will charge 40% of the contract vale for service tax computation purpose. Further the sub-contarctor also charge on us 40% of vale of sub-contract. 

Further we will pay 50% under reverse charge basis since we are company.

can we avail the input credit on both 40% of the sub-contract value and 50% under reverse charge.

please reply urgently.

Dear Sir , 

We are working in Military Engineering Services as a Contractor . Till now we are exempted for service tax but now in 2015 budget we have to pay service tax .But we dont know on what amount we have to pay service tax . some says service tax is payable on check amount , some says it is payable on labour charges but nothing was confirm. so please help me inthis matter