Reverse credit of input vat against cst sales(tamilnadu)

Iyappan R (Manager Accounts) (53 Points)

18 April 2014  
Dear Sir,
We are a registered dealer manufacturer unit in Tamil Nadu. we have purchase the Raw material from- Otherstate 70% & tamil nadu 30% we have sales the finished goods to otherstate 90% & 10% tamil nadu. Other state sales means CST sales2% with C form. we need to reverse the Credit on purchase with in the state.
If Its Correct please sensd the Formula for the above.
Please help me in this regards,
R.Iyappan
Cell: 9894818701