Estoppel - Proprietary Estoppel. Madi v. King
In Madi v. King (Ont CA, 2023) the Court of Appeal considered proprietary estoppel, here in a family separation case where the value of the matrimonial home increased from the date of separation to the actual sale:
 The leading case governing proprietary estoppel is the Supreme Court’s decision in Cowper-Smith. That decision, which was not a family law case, set out the following test, at para. 15:
An equity arises when (1) a representation or assurance is made to the claimant, on the basis of which the claimant expects that he will enjoy some right or benefit over the property; (2) the claimant relies on that expectation by doing or refraining from doing something, and his reliance is reasonable in all the circumstances; and (3) the claimant suffers detriment as a result of his reasonable reliance, such that it would be unfair or unjust for the party responsible for the representation or assurance to go back on her word. [Citations omitted.] The claimant must establish all three elements of the test: Cowper-Smith, para. 23.
 There is no evidence of any detriment suffered by the respondent by reliance on the assurance or expectation that she was an equal owner. She did not contribute either to the mortgage or to the expenses of running the home, nor did she change her position in any other material way. Notably, in the only Ontario case which appears to have applied the doctrine of proprietary estoppel to a post-valuation date increase in the value of the matrimonial home, the wife, who had thought she was on title, was registered on the mortgage and had contributed $120,000 to the purchase of the home, which the court found to have constituted detrimental reliance: Spadacini-Kelava v. Kelava, 2020 ONSC 7907, 52 R.F.L. (8th) 143, leave to appeal to Ont. C.A. refused, M52096.
 Here, not only was there no evidence of detrimental reliance, but the respondent received countervailing benefits in the sense applied in the case of Scholz v. Scholz, 2013 BCCA 309, 46 B.C.L.R. (5th) 98, at para. 33. Specifically, the appellant allowed her to continue to live in the house without paying rent or contributing to the mortgage for several months after they separated.