“The principles applicable to a motion for leave to appeal a costs order are set out in Van v. Palombi, 2015 ONSC 170 and Eustace v. Eustace, 2017 ONSC 4814 and are as follows.
Pursuant to section 133(b) of the Courts of Justice Act leave is required where an appeal relates only to costs that are in the discretion of the court.
Rule 62.02(4) of the Rules of Civil Procedure provides as follows:
Leave to appeal shall not be granted unless, (a) there is a conflicting decision by another judge or court in Ontario or elsewhere on a matter involved in the proposed appeal and it is, in the opinion of the judge hearing the motion, desirable that leave to appeal be granted; or (b) there appears to the judge hearing the motion good reason to doubt the correctness of the order in question and the proposed appeal involves matters of such importance that, in his or her opinion, leave to appeal should be granted.
There is considerable defence owed by an appellate court to costs orders made. Leave to appeal should only be granted sparingly and “there must be some indication of a complete failure to exercise discretion or an exercise of discretion based on an erroneous principle”.
The test is not whether the appellate court would have made a different decision but whether the motions judge based the exercise of discretion on an error of principle or was clearly wrong: Van v. Palombi at para 5.
With respect to public importance, “these words refer to matters of general importance, not. Matters of particular importance relevant only to the litigants. General importance relates to matters of public importance and matters relevant to the development of the law and the administration of justice”: Greslik v. Ontario Legal Aid Plan (1988), 1988 CanLII 4842 cited in Van v. Palombi at para 5.”
E.C. v. P.A., 2022 ONSC 1163 (CanLII) at 4-9