Can a Judge Reconsider a Decision Where It Appears That a Mistake Was Made?
Generally, When a Judicial Decision Is Rendered the Matter Is Considered Final and May Be Corrected Only Upon An Appeal to a Higher Court. Only In Rare Circumstances, Such As When the Error Is Obvious and All Parties Involved Agree to a Reconsideration, Will a Judge Review a Prior Decision.
Understanding When It May Be Appropriate to Ask a Judge to Reconsider a Court Decision
The legal process that involves the court making a judicial decision is intended to finalize matters in dispute. Accordingly, once a case is decided the law expects that all involved will respect the decision, including any mistakes within the decision, unless taken by Appeal to a higher court. As such, it is very rare that a Judge will reconsider a decision.
Generally, a court has the jurisdiction to control its process which includes the power to review a decision of itself; however, whether a court should review a decision of itself still remains questionable and should occur only where it becomes obvious to the court and parties that a decision was flawed and the parties consent to a reconsideration. This issue was specifically addressed within the case of Gupta v. Lindal Cedar Homes Ltd., 2020 ONSC 7524 wherein it was said:
 The court has an inherent jurisdiction to adjust a litigation result after judgment in some circumstances, other than through proper appellate review or as contemplated by r. 59.06. However, this should occur only in “unusual and rare circumstances where the interests of justice compel such a result”: Susin v. Chapman,  O.J. No. 2935 (C.A.), at para. 10. Finality in litigation is to be encouraged and fostered. The discretion to re-open a matter should be resorted to “sparingly and with the greatest care”: 671122 Ontario Ltd. v. Sagaz Industries Canada Inc., 2001 SCC 59 (CanLII),  2 S.C.R. 983, at para. 61.
 In Schmuck v. Reynolds-Schmuck (2000), 2000 CanLII 22323 (ON SC), 46 O.R. (3d) 702 (S.C.J.) at para. 25, Himel, J. emphasized the limited circumstances in which a reconsideration should occur, stating: “It is my view that a party who wishes a reconsideration would have to establish that the integrity of the litigation process is at risk unless it occurs, or that there is some principle of justice at stake that overrides the value of finality in litigation, or that some miscarriage of justice would occur if such a reconsideration did not take place.”
 In Gore Mutual Insurance Co. v. 1443249 Ontario Ltd., (2004) 2004 CanLII 27736 (ON SC), 70 O.R. (3d) 404 (“Gore”), at paras. 7-8, Karakatsanis, J. (as she then was) was prepared to re-open her decision in a situation where it was “obvious an error was made by all counsel and by the court.” It was a “case of a clear error.” It was “obvious” that the statutory provision now raised would have changed her determination and all counsel conceded that the provision previously relied upon had no application to the case. Karakatsanis, J. concluded at para. 8 that the “interests of justice are not served by requiring an appeal on a clear error of law that followed inaccurate and incomplete legal submissions of counsel.”
 In Scott, Pichelli & Easter Ltd. et al. v. Dupont Developments Ltd. et al., 2019 ONSC 6789, Sossin, J. (as he then was) noted at para. 13 that a “motion for reconsideration is more likely to be successful where the parties agree that an error has occurred, and less likely to be successful where the subject matter of the alleged error remains contested by the parties.”
As indicated, unless all parties consent to a reconsideration, and unless it appears obvious that an error was made, it is likely that a judge will decline a request to reconsider a decision and thereby a decision will stand unless appealed.
Generally, when a court makes a decision, the decision becomes final and is subject to reversal or correction only via an appeal and only in some very limited circumstances may a judge be willing to reconsider a previously rendered decision.