18.—(1) Paragraphs (2) and (3) apply where, by reason of a change in the regular interval at which any part of an earner’s earnings is paid or treated as paid in respect of employed earner’s employment (“the regular interval of payment”), that person’s earnings period in any employment or employments under the same secondary contributor is, or is in the process of being, changed.
(2) Subject to paragraph (3), in relation to any payments made on or after the date of change the earnings period shall be determined in accordance with the new interval.
(3) Where the new period is longer than the old period and during the first new period any payment has also been made at the old interval, the earnings-related contributions payable on any payment made on or after the date of change shall not exceed in amount the total which would have been payable if all the payments during the new period had been made at the new interval.
(4) In this regulation—
(a)the regular interval of payment which has been discontinued is referred to as “the old interval” and the interval which has, or is to, become the regular interval of payment is referred to as “the new interval”;
(b)the earnings period determined according to the old interval is referred to as “the old period” and that determined according to the new interval is referred to as “the new period”;
(c)reference to payment means payment of earnings actually made or, as the case may be, treated under regulation 7 as made, at an interval or date; and
(d)“date of change” means the date on which the first payment of earnings at the new interval is made.