Regarding vat credit

We have made purchases from various registered dealers. But we have not mentioned their details in our TNVAT returns. The person from whom the purchase is made has paid output tax. He has mentioned my TIN in the Annexure II of Form I (where we mention the sales). My query is whether we can claim input tax credit on the purchases made since the person from whom the purchase is made already paid the tax. If i didn't mention the purchase details in my VAT returns why should i pay the tax twice 1) Once at the time of purchase i will be paying to the seller 2) Secondly due to inability to claim input VAT credit i will be paying excess amount of tax. In case of Direct tax, if the person deducted TDS and paid it to the government it will be reflected in Form 26AS by reference to PAN. Why is there no such mechanism in sales tax by reference to TIN of Buyer.