What is the common law test for a change in the amount of maintenance awarded by the Court of Appeal?

From a general perspective, parents have a joint and an ongoing legal obligation to support their children. It is the child, not the other parent, who has the right to maintenance. The payment of maintenance is based not just on what a parent does earn, but what he or she can earn. A change to the Guidelines amount is not automatic. Earle v. Earle, at page 7, paragraph 46.

Insofar as arrears are concerned, Earle v. Earle provides the following examples: a. Arrears will only be cancelled if the person is unable to pay now and will be unable to pay in the future. b. A reduction or a cancellation requires detailed and full financial disclosure, under oath (usually in the form of an affidavit) that at the time the payments were to be made: i. the change was significant and long lasting and ii. the change was real and not one of choice and iii. every effort was made to earn money (or more money) during the time in question, and those efforts were not successful.