For the purposes of section 67, if:
(a) the Registrar has entered an initial period in the Register under paragraph 26(2)(a) in respect of a liability; and
(b) a child support debt in respect of a payment period for the liability becomes due and payable on a particular day (the payment period due day ); and
(c) the payment period due day occurs before any day on which a child support debt in respect of a day in the initial period for the liability is due and payable;
the child support debt in respect of the payment period is taken to have become due and payable on the day on which a child support debt in respect of the last day in the initial period is due and payable.