Deductible sales tax: deferred or government-retained sales tax reduces assessable value under central excise law. Where sales tax is not payable by law (exemption) it cannot be deducted from the wholesale price; however, sales tax that is deferred or treated as payable because a State incentive credits an equivalent amount as payment is considered payable by the assessee and is deductible from the wholesale price for determination of assessable value for central excise duty.