(1) Where on an application made under this section in relation to an order to which this section applies it appears to the Court that by reason of—
(a) a change in the circumstances of the person entitled to, or liable to make, payments under the order since the order was made; or
(b) the changed circumstances resulting from the death of the person so liable,
the amount received by the person entitled to payments under the order in respect of a period after those circumstances changed or after the death of the person liable to make payments under the order as the case may be, exceeds the amount which the person so liable or his or her personal representative should have been required to pay, the Court may order the respondent to the application to pay to the applicant such sum, not exceeding the amount of the excess, as the Court thinks just.
This section applies to an order made by virtue of section 21, 22(1)(a) or 22(1)(b), 23(2)(a) or 23(2)(b), 26(5) or 26(6)(a), 26(6)(b), 26(6)(d) or 26(6)(e).
(2) An application under this section may be made by the person liable to make payments under an order to which this section applies or his or her personal representatives and may be made against the person entitled to payments under the order or his or her personal representatives.
(3) An application under this section may be made in proceedings for—
(a) the variation or discharge of the order to which this section applies; or
(b) leave to enforce, or the enforcement of the payment of arrears under that order.
(4) An order under this section for the payment of any sum may provide for the payment of that sum by instalments of such amount as may be specified in the order.