Notwithstanding anything contained in this Act, if the Commissioner is of the opinion that any transaction by any dealer during any tax period or a set of transactions by the dealer has been accounted in a manner so as to pay tax less than the tax otherwise payable on such sale or purchase, then the Commissioner shall calculate the tax liability as per fair market price of such transaction or transactions.

Explanation.-For the purpose of this section, "fair market price" means the value at which goods of like kind are sold or would be sold in the open market in the State.