Net tax calculation: output tax less input credit and carry forward, with surplus adjusted against sales tax or refunded. Net tax for a tax period equals output tax minus input tax credit minus any carried forward amount. A negative net tax must first be adjusted against Central Sales Tax liability in the same period; any remaining excess may be carried forward to the next calendar month or tax period or claimed as a refund at the end of a tax period, with refunds processed by the Commissioner. Refunds are claimable only at period end and inadvertent excess payments are treated as credit. The provision has been amended to modify carry forward and refund rules.