s 45 Addition or deduction of new or altered duties in the case of contract
(1) Where any new excise duty is imposed or where any excise duty is increased, and any goods in respect of which the duty is payable are delivered after the day on which the new or increased duty takes effect in pursuance of a contract made before that day, the seller of the goods may, in the absence of agreement to the contrary, recover as an addition to the contract price a sum equal to any amount paid by him in respect of the goods on account of the new duty or increase of duty, as the case may be. (2) Where any excise duty is cancelled or decreased and any goods affected by the duty are delivered after the day on which the duty is cancelled or the decrease in the duty takes effect in pursuance of a contract made before that day, the purchaser of the goods may, in the absence of agreement to the contrary and if the seller of the goods has had in respect of those goods the benefit of the cancellation or decrease of the duty, deduct from the contract price a sum equal to the amount of duty or decrease of duty, as the case may be.