What is the test for retroactivity in a child maintenance application?

This Court continued (at para. 31): However, it should be noted that these “exceptional circumstances” referred to in Wilkinson are required only when an order of retroactivity is sought which encompasses the time period preceding the filing of the initial application. For example, in Wilkinson, the custodial parent sought a variation of maintenance that was to extend back over the entire period of time between the date of the original order and the date of the variation order. In that circumstance, the blameworthiness of the payor and diligence on the part of the payee are relevant and the rule makes good sense. It is based on the proposition that there is a presumption that a previous court order is to be respected [see: Willick v. Willick, 1994 CanLII 28 (SCC), [1994] 3 S.C.R. 670].