‘Mutual Wills’ refer to Last Will and Testaments executed by two individuals, typically spouses, predicated on the contractual agreement and understanding that both parties will not change, or revoke their Wills, often to ensure specific beneficiaries receive their estate. The following is a high-level summary of the Mutual Wills doctrine and how it operates in practice.
Key Requirements
The origins of the doctrine trace back to the English case of, Dufour v. Pereira (1769), which established that, where Mutual Wills were found to exist, equity will enforce this agreement by imposing a trust upon the survivor’s estate.[1]
In Edell v. Sitzer,[2] Justice Cullity of the Ontario Superior Court provided a thorough overview of the Mutual Wills doctrine:
The doctrine of mutual wills has traditionally been applied in cases where individuals have made separate wills pursuant to an agreement with respect to their terms. Most commonly, they have agreed that each will obtain a benefit under the other’s will and that other specified individuals will receive property of each of them on the death of the survivor. In some cases of this sort, the benefit obtained by the survivor under the other’s will has been a life interest; in other cases, it takes the form of an outright gift. Where the requirements for the application of the doctrine are satisfied, the survivor will not be permitted to defeat the agreement by revoking his or her will after the death of the other. This result is achieved by the imposition of a constructive trust on the survivor’s estate for the benefit of those who intended to benefit under the agreement.[3] [emphasis added]
Accordingly, for the Mutual Wills doctrine to apply, three factors are required:
- There must be an agreement between the individuals who made the wills, which amounts to a contract at law;
- The agreement must be proven by clear and satisfactory evidence; and
- It must include an agreement not to revoke their wills.[4]
The requirements for determining the existence of such an agreement are governed by the general enforceability of a contract.[5].
The Ontario Court of Appeal (“ONCA”) has highlighted that the onus of proving Mutual Will rests with the party alleging their existence. In this regard, while the legal onus is proof on the balance of probabilities, the quality of the evidence “must be clear and cogent”.[6]
Due to the far-reaching consequences of finding a Mutual Will agreement exists, the court will not generally make a finding of intention lightly. To ascertain the intention of the parties, the court will examine the four corners of the will as well as extrinsic evidence.[7]
It is worth remembering that section 13 of Ontario’s Evidence Act,[8] provides that a verdict cannot be obtained on the evidence of a potential beneficiary of the verdict unless that evidence is corroborated by other material evidence:
13 In an action by or against the heirs, next of kin, executors, administrators or assigns of a deceased person, an opposite or interested party shall not obtain a verdict, judgment or decision on his or her own evidence in respect of any matter occurring before the death of the deceased person, unless such evidence is corroborated by some other material evidence.
In the event it becomes necessary to enforce a Mutual Wills agreement, the law of equity will impose a constructive trust. The purpose of equity intervening with a constructive trust is, “to enforce the survivor’s promise to the deceased to confer a benefit on the beneficiaries of the mutual will”.[9]
Applications in Case Law
Neilson v. Trottier
In Neilson v. Trottier,[10] a husband and wife in their second marriage, executed Mutual Wills and entered into an agreement not to revoke or amend them. The agreement included all current and future property and revoked any prior cohabitation agreements. They acknowledged that breaching their agreement would result in a constructive trust favoring their children.[11]
After the husband’s death, the widow donated $200,000 to a college in his honour. The court examined whether this gift breached the couple’s Mutual Wills agreement. The Application judge, referencing Edell v. Sitzer, found that the gift was intended to honor the deceased husband, not to defeat the Mutual Wills agreement. Therefore, the widow did not breach the agreement, and no constructive trust was necessary.[12]
Jackson v. Rosenberg
In Jackson v. Rosenberg (“Jackson”),[13] the court dismissed a claim of a Mutual Wills agreement for lack of corroborating evidence. Jackson concerned Mr. Taube, and Mr. Jackson, who were partners since in or around 1963. In 2005, both executed mirror wills, naming each other as the sole beneficiary of their respective estates. Mr. Taube also listed his great niece, Ms. Rosenberg as his alternate beneficiary given he had no other family to support.[14]
It was Ms. Rosenberg’s position that Mr. Taube and Mr. Jackson executed a binding Mutual Wills agreement, relying on the mirrored terms in their respective wills. The application judge found no direct written or oral confirmation of such an agreement, noting Mr. Jackson’s express denial of one, and relied on evidence that Mr. Taube had altered his will after 2005 (executing a codicil in 2009). In this regard, the Application Judge relied on the decision in Gefen,[15] where the ONCA noted that:
A mutual will agreement is more than a mirror will — it is an agreement that the wills are not changed and is a constraint on testamentary freedom. The testamentary intentions of the will-makers expressed in their mirror wills is not enough to establish that they had agreed that the survivor would not be able to vary such dispositions in the future.[16] [emphasis added]
Concluding Comments
In summary, the Mutual Wills doctrine ensures that a contractual agreement between parties to not revoke their wills is upheld by imposing a constructive trust on the survivor’s estate, thereby protecting the intended beneficiaries’ interests. This doctrine requires a clear and satisfactory agreement, proven by cogent evidence, to prevent the survivor from altering the testamentary dispositions after the other party’s death.
—
[1] Fox, Re, 1951 CarswellOnt 53 at para 8.
[2] Edell v. Sitzer, 2001 CanLII 27989 (ON SC) (“Edell”).
[3] Ibid. at para 58.
[4] Edell at para 58.
[5] Trotman v. Thompson, 2006 CarswellOnt 1056 at para 46.
[6] Gefen Estate v. Gefen, 2022 ONCA 174 at para 37 (“Gefen”).
[7] Gefen at para 31.
[8] Evidence Act, R.S.O. 1990, c. E.23 at section 13.
[9] Edell at para 62.
[10] Neilson v. Trottier, 2019 ONSC 1657.
[11] Ibid. at paras 5 – 16.
[12] Ibid. at paras 51 – 53.
[13] Jackson v. Rosenberg, 2023 ONSC 4403 (CanLII) (“Jackson”); dismissed on appeal in Jackson v. Rosenberg, 2024 ONCA 875 (CanLII).
[14] Ibid. at para 13.
[15] Gefen v. Gaertner, 2019 ONSC 6015, at para. 80 aff’d Gefen Estate v. Gefen, 2022 ONCA 174.
[16] Jackson at paras 108 – 112.
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Written by: Oliver O'Brien
Posted on: October 1, 2025
Categories: Commentary, WEL Newsletter
‘Mutual Wills’ refer to Last Will and Testaments executed by two individuals, typically spouses, predicated on the contractual agreement and understanding that both parties will not change, or revoke their Wills, often to ensure specific beneficiaries receive their estate. The following is a high-level summary of the Mutual Wills doctrine and how it operates in practice.
Key Requirements
The origins of the doctrine trace back to the English case of, Dufour v. Pereira (1769), which established that, where Mutual Wills were found to exist, equity will enforce this agreement by imposing a trust upon the survivor’s estate.[1]
In Edell v. Sitzer,[2] Justice Cullity of the Ontario Superior Court provided a thorough overview of the Mutual Wills doctrine:
The doctrine of mutual wills has traditionally been applied in cases where individuals have made separate wills pursuant to an agreement with respect to their terms. Most commonly, they have agreed that each will obtain a benefit under the other’s will and that other specified individuals will receive property of each of them on the death of the survivor. In some cases of this sort, the benefit obtained by the survivor under the other’s will has been a life interest; in other cases, it takes the form of an outright gift. Where the requirements for the application of the doctrine are satisfied, the survivor will not be permitted to defeat the agreement by revoking his or her will after the death of the other. This result is achieved by the imposition of a constructive trust on the survivor’s estate for the benefit of those who intended to benefit under the agreement.[3] [emphasis added]
Accordingly, for the Mutual Wills doctrine to apply, three factors are required:
The requirements for determining the existence of such an agreement are governed by the general enforceability of a contract.[5].
The Ontario Court of Appeal (“ONCA”) has highlighted that the onus of proving Mutual Will rests with the party alleging their existence. In this regard, while the legal onus is proof on the balance of probabilities, the quality of the evidence “must be clear and cogent”.[6]
Due to the far-reaching consequences of finding a Mutual Will agreement exists, the court will not generally make a finding of intention lightly. To ascertain the intention of the parties, the court will examine the four corners of the will as well as extrinsic evidence.[7]
It is worth remembering that section 13 of Ontario’s Evidence Act,[8] provides that a verdict cannot be obtained on the evidence of a potential beneficiary of the verdict unless that evidence is corroborated by other material evidence:
13 In an action by or against the heirs, next of kin, executors, administrators or assigns of a deceased person, an opposite or interested party shall not obtain a verdict, judgment or decision on his or her own evidence in respect of any matter occurring before the death of the deceased person, unless such evidence is corroborated by some other material evidence.
In the event it becomes necessary to enforce a Mutual Wills agreement, the law of equity will impose a constructive trust. The purpose of equity intervening with a constructive trust is, “to enforce the survivor’s promise to the deceased to confer a benefit on the beneficiaries of the mutual will”.[9]
Applications in Case Law
Neilson v. Trottier
In Neilson v. Trottier,[10] a husband and wife in their second marriage, executed Mutual Wills and entered into an agreement not to revoke or amend them. The agreement included all current and future property and revoked any prior cohabitation agreements. They acknowledged that breaching their agreement would result in a constructive trust favoring their children.[11]
After the husband’s death, the widow donated $200,000 to a college in his honour. The court examined whether this gift breached the couple’s Mutual Wills agreement. The Application judge, referencing Edell v. Sitzer, found that the gift was intended to honor the deceased husband, not to defeat the Mutual Wills agreement. Therefore, the widow did not breach the agreement, and no constructive trust was necessary.[12]
Jackson v. Rosenberg
In Jackson v. Rosenberg (“Jackson”),[13] the court dismissed a claim of a Mutual Wills agreement for lack of corroborating evidence. Jackson concerned Mr. Taube, and Mr. Jackson, who were partners since in or around 1963. In 2005, both executed mirror wills, naming each other as the sole beneficiary of their respective estates. Mr. Taube also listed his great niece, Ms. Rosenberg as his alternate beneficiary given he had no other family to support.[14]
It was Ms. Rosenberg’s position that Mr. Taube and Mr. Jackson executed a binding Mutual Wills agreement, relying on the mirrored terms in their respective wills. The application judge found no direct written or oral confirmation of such an agreement, noting Mr. Jackson’s express denial of one, and relied on evidence that Mr. Taube had altered his will after 2005 (executing a codicil in 2009). In this regard, the Application Judge relied on the decision in Gefen,[15] where the ONCA noted that:
A mutual will agreement is more than a mirror will — it is an agreement that the wills are not changed and is a constraint on testamentary freedom. The testamentary intentions of the will-makers expressed in their mirror wills is not enough to establish that they had agreed that the survivor would not be able to vary such dispositions in the future.[16] [emphasis added]
Concluding Comments
In summary, the Mutual Wills doctrine ensures that a contractual agreement between parties to not revoke their wills is upheld by imposing a constructive trust on the survivor’s estate, thereby protecting the intended beneficiaries’ interests. This doctrine requires a clear and satisfactory agreement, proven by cogent evidence, to prevent the survivor from altering the testamentary dispositions after the other party’s death.
—
[1] Fox, Re, 1951 CarswellOnt 53 at para 8.
[2] Edell v. Sitzer, 2001 CanLII 27989 (ON SC) (“Edell”).
[3] Ibid. at para 58.
[4] Edell at para 58.
[5] Trotman v. Thompson, 2006 CarswellOnt 1056 at para 46.
[6] Gefen Estate v. Gefen, 2022 ONCA 174 at para 37 (“Gefen”).
[7] Gefen at para 31.
[8] Evidence Act, R.S.O. 1990, c. E.23 at section 13.
[9] Edell at para 62.
[10] Neilson v. Trottier, 2019 ONSC 1657.
[11] Ibid. at paras 5 – 16.
[12] Ibid. at paras 51 – 53.
[13] Jackson v. Rosenberg, 2023 ONSC 4403 (CanLII) (“Jackson”); dismissed on appeal in Jackson v. Rosenberg, 2024 ONCA 875 (CanLII).
[14] Ibid. at para 13.
[15] Gefen v. Gaertner, 2019 ONSC 6015, at para. 80 aff’d Gefen Estate v. Gefen, 2022 ONCA 174.
[16] Jackson at paras 108 – 112.
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