40.— (1) The Minister shall calculate in accordance with this section the amount of levy payable in respect of a month by each oil company and oil consumer liable to pay the levy on its relevant disposals in the month and shall notify the Agency of that amount.

(2) The amount of levy shall be calculated by reference to—

(a) the oil company’s or the oil consumer’s relevant disposals of petroleum products (including, where appropriate, of each category of petroleum products) in the month as specified in its volume assessment for the month, and

(b) F56[the rate of levy specified in section 37(1A).]