Stays - Conflicting Proceedings [R21.01(3)(c)]. Unoh v. Agboola
In Unoh v. Agboola (Div Court, 2023) the Divisional Court considered a stay, here in family law proceedings:
Guiding Principles – Order to Stay. Hutton v. Sayat
 Rule 2 specifies that the primary objective of the Rules is to enable the court to deal with cases justly. In dealing with a case justly, the court is required to:
a. Ensure that the procedure is fair to all parties; The Rules must be applied in a way that promotes the primary objective which involves active case management by the court. Parties and their lawyers are required to assist the court in promoting the primary objective.
b. Save time and expense;
c. Deal with a case in ways that are appropriate to its importance and complexity; and
d. Give appropriate court resources to the case while taking account of the need to give resources to other cases.
 Section 106 of the Courts of Justice Act, R.S.O. 1990, c. C-43, as amended (the “CJA”), allows a court to stay a proceeding on such terms as are considered just. The court’s mandate under rule 2(5) to take active management of cases will occasionally require consideration of the courts power to stay proceedings under section 106 of the CJA.
In Hutton v. Sayat (Fed CA, 2023) the Federal Court of Appeal cites grounds for ordering a stay of proceedings:
 Subsection 50(1) of the Federal Courts Act, R.S.C. 1985, c. F-7, grants this Court and the Federal Court the authority to stay a proceeding when a claim is being proceeded with in another court, or where it is in the interest of justice that the procedure be stayed. As noted by Justice Fothergill, the interest of justice has been interpreted broadly, and is not limited to the interests of the party but rather includes a consideration of the integrity of the judicial process: Canada (Minister of Citizenship and Immigration) v. Tobiass, 1997 CanLII 322 (SCC),  3 S.C.R. 391 at paras. 88-90; Pearson v. Canada, 1999 CanLII 8631 (FC) at paras. 20-23.. Kilian v. CPSO
In Kilian v. CPSO (Div Court, 2023) the Divisional Court considers the criteria for a stay, here where it's in response to a competing proceeding:
 Counsel for Dr. Kilian is correct in his observation that the granting of a stay is a discretionary remedy. However, judicial discretion has its limits. The test for granting an interim stay of one proceeding until another is resolved is set out in numerous cases, including the recent decision of Crosslinx v. Ontario Infrastructure 2021 ONSC 3567 at paras. 37-38:. Birdseye Security Inc. v. Milosevic
a) Whether there is substantial overlap of issues in the two proceedings;
b) Whether the two cases share the same factual background;
c) Whether issuing a temporary stay will prevent unnecessary and costly duplication of judicial and legal resources; and
d) Whether the temporary stay will result in an injustice to the party resisting the stay.
In Birdseye Security Inc. v. Milosevic (Ont CA, 2020) the Court of Appeal considered when a stay could issue in an action because otherwise it would prejudice another action:
 A defendant may move for an order staying or dismissing an action (in this case a counterclaim) under r. 21.01(3)(c) where “another proceeding is pending in Ontario or another jurisdiction between the same parties in respect of the same subject matter”. Having concluded that the duplicative counterclaim justified a stay, the motion judge ought to have stayed, and not “struck” the counterclaim. No issue was made of this, and nothing turns on it for the purpose of the appeal. Rather, the issue is whether there was a reversible error in the application of r. 21.01(3)(c) to bring to an end the counterclaim in Action 4669.
 The determination of whether a stay of proceedings should be granted because another proceeding is pending between the same parties involves an exercise of discretion, taking into consideration the circumstances of the particular case. The moving party must demonstrate that the continuation of the action would cause it substantial prejudice or injustice (beyond inconvenience and expense) because it would be oppressive or vexatious or would otherwise be an abuse of the process of the court, and that the stay would not cause an injustice to the responding party: Farris v. Staubach Ontario Inc. (2004), 2004 CanLII 11325 (ON SC), 32 C.C.E.L. (3d) 265 (Ont. S.C.), at para. 15. Factors relevant to prejudice include: the likelihood and effect of the two matters proceeding in tandem, the possibility and effect of different results, the potential for double recovery, and the effect of possible delay: Farris, at para. 16.
 The fact that another proceeding is pending between the same parties in respect of the same subject matter does not automatically lead to an order dismissing or staying the claim. Rather, the order is discretionary and the judge hearing the motion must be satisfied that the stay or dismissal is warranted in the particular circumstances of the case. While a multiplicity of proceedings may constitute an abuse of process which warrants an order staying or dismissing a proceeding (see e.g., Maynes v. Allen-Vanguard Technologies Inc. (Med-Eng Systems Inc.), 2011 ONCA 125, 274 O.A.C. 229, at paras. 36, 46), that is not necessarily always the case. All of the circumstances must be considered to determine whether, in the interests of justice, a stay or dismissal should be granted.
 In this case, the motion judge stayed the counterclaim “to avoid an unjust multiplicity of proceedings”. He concluded that the duplicative litigation would “on the facts of this case” constitute an abuse of process, and he rejected Mr. Milosevic’s claim of prejudice on the basis that he would be able to pursue his counterclaim in Action 1527 regardless of whether Birdseye discontinued the main action in that proceeding.
 An order dismissing or staying a proceeding under r. 21.01(3)(c) is a discretionary order that is subject to deference on appeal, absent an error in principle: 1420041 Ontario Inc. v. 1 King West Inc., 2010 ONSC 6671, 1 R.P.R. (5th) 33 (Div. Ct.), at para. 24, rev’d on other grounds 2012 ONCA 249, 349 D.L.R. (4th) 97, leave to appeal refused,  S.C.C.A. No. 272; Canada (Minister of Citizenship and Immigration) v. Tobiass, 1997 CanLII 322 (SCC),  3 S.C.R. 391, at para. 87.