¹[64A. In the event of any duty of customs or excise or tax on any goods being imposed, increased, decreased or remitted after the making of any contract for the sale of such goods without stipulation as to the payment of duty or tax where duty or tax was not chargeable at the time of the making of the contract, or for the sale of such goods duty-paid or tax-paid where duty or tax was chargeable at the time,-(a) if such imposition or increase so takes effect that the duty or tax or increased duty or tax, as the case may be, or any part thereof, is paid, the seller may add so much to the contract price as will be equivalent to the amount paid in respect of such duty or tax or increase of duty or tax, and he shall be entitled to be paid and to sue for and recover such addition, and (b) if such decrease or remission so takes effect that the decreased duty or tax only or no duty or tax, as the case may be, is paid, the buyer may deduct so much from the contract price as will be equivalent to the decrease of duty or tax or remitted duty or tax, and he shall not be liable to pay, or be sued for or in respect of, such deduction.] Explanation. The word "tax" in this section means the tax payable under the Sales Tax Act,1951.