What is the test for a parent to apply for a change in custody?

A parent applying for a change in custody must meet the threshold requirement of demonstrating a material change in the circumstances affecting the child. More specifically, before entering on the merits of an application to vary a custody order the judge must be satisfied of three things: (1) a change in the condition, means, needs or circumstances of the child and/or ability of the parents to meet the needs of the child; (2) which materially affects the child; and (3) which was either not foreseen or could not have been reasonably contemplated by the judge who made the initial order. If the threshold is met, the judge on the application must embark on a fresh inquiry into what is in the best interests of the child, having regard to all the relevant circumstances relating to the child's needs and the ability of the respective parents to satisfy them: Gordon v. Goertz, [1996] 2 S.C.R. 27, 1996 CanLII 191 at para. 13. This inquiry is based on the findings of the judge who made the previous order and evidence of the new circumstances: ibid. at para. 17.