“Section 56(4) of the FLA sets out when a domestic contract can be set aside. The court may set aside a domestic contract or a provision in it if a party failed to disclose to the other, significant assets, debts or other liabilities existing when the domestic contract was made; if a party did not understand the nature or consequences of the contract; or otherwise in accordance with the law of contract.
Courts have discretion in setting aside Minutes of Settlement. The most common factors for consideration are whether there had been a concealment of assets or material misrepresentation; whether there had been duress, or unconscionable circumstances; whether the petitioning party neglected to pursue full legal disclosures; whether the petitioning party moved expeditiously to have the agreement set aside; whether the petitioning party received substantial benefits under the agreement; whether the other party had fulfilled his or her obligations under the agreement; and whether the non-disclosure was a material inducement to entering the agreement. In other words, how important was the non-disclosed information to the negotiation? See Dochuk v. Dochuk (1999), 1999 CanLII 14971 (ON SC), 44 R.F.L. (4th) 97 (Ont. Div. Ct.), at para. 17.
In determining whether a contract should be set aside, the court must first consider whether the party seeking such can demonstrate one or more of the circumstances outlined in s. 56(4) and if so, whether it is appropriate to set aside the agreement: see LeVan v. LeVan, 2008 ONCA 388, [2015] O.J. No. 4883. In Hartshorne v. Hartshorne, 2004 SCC 22, [2004] 1 S.C.R. 550, the Supreme Court of Canada held that courts should respect private agreements reached between spouses.
The burden is on the party seeking to set aside the agreement, in this case the mother, to bring herself within one of the paragraphs of s. 56(4) and then to persuade the court to exercise its discretion to set aside the agreement: see LeVan; see also Dougherty v. Dougherty, 2008 ONCA 302, 89 O.R. (3d) 760.”