(1) The due day for payment of the levy,—
(a) by a collection agent, is the day on which the collection agent is liable to pay the grower for the wheat grain or wheat grain product:
(b) by a grower, is the day on which the grower is paid for the wheat grain or wheat grain product sold by the grower.
(2) The latest day for payment is,—
(a) in the case of a payment required under subclause (1)(a), the 20th day of the following month:
(b) in the case of a payment required under subclause (1)(b), the 20th day of the second month following that in which the grower is paid for the wheat grain or wheat grain product.