If:
(a) a payer of an enforceable maintenance liability makes an election of a kind set out in section 65A; and
(b) the Registrar is satisfied that it will be more convenient for the payer to accrue debts in relation to the elected period instead of the period in the Child Support Register;
the Registrar must, within 28 days of receiving the election, vary the particulars of the entry in the Register in relation to the payment period by:
(c) substituting the elected period; and
(d) entering in the Register the specified day as the day from which the period starts.