What is the test for altering the terms of a valid marriage agreement?

Miglin imposes a two-stage inquiry into the issue of altering the terms of a valid separation agreement in the context of an application under either s. 15 or s. 17 of the Divorce Act. First, there must be a “material change in circumstances” since the parties entered into the agreement. The threshold of what constitutes a “material change in circumstances” remains as Sopinka J. defined it in Willick v. Willick, 1994 CanLII 28 (SCC), [1994] 3 S.C.R. 670, at p. 688, 119 D.L.R. (4th) 405: In deciding whether the conditions for variation exist, it is common ground that the change must be a material change of circumstances. This means a change, such that, if known at the time, would likely have resulted in different terms. The corollary to this is that if the matter which is relied on as constituting a change was known at the relevant time it cannot be relied on as the basis for variation…