Mutual Wills in British Columbia: When a Will Becomes Irrevocable

Mutual wills occupy a unique area of estate law in British Columbia. While many spouses prepare “mirror wills” that leave everything to one another, not every pair of similar wills creates a binding obligation.  A mutual will can significantly restrict the surviving spouse’s ability to later change their estate plan. 

Where a valid mutual wills agreement exists, equity may intervene to prevent the survivor from defeating the original agreement after the first will-maker dies. In some cases, the court may impose a constructive trust over estate assets or permit tracing claims against third parties who received property in breach of the agreement.

What Is a Mutual Will?

A mutual will arises where two individuals agree to make wills in particular terms and further agree that those wills will not be revoked without the consent of the other.

Mutual wills most commonly arises between spouses, particularly in blended family situations where each spouse wishes to ensure that certain beneficiaries, often children from prior relationships, ultimately inherit specific property after both spouses have died.

Importantly, a mutual wills agreement is not created merely because two wills contain similar or identical terms, there must be a binding agreement not to revoke the wills.

For a mutual wills agreement to become enforceable, the first will-maker must die without revoking or altering their will in breach of the agreement. A revocation is not valid if it is not an “open act” done during the life-time of both will-makers.

To establish the existence of a mutual wills agreement, the court must be satisfied that:

  • there was an agreement between the will-makers amounting to an enforceable contract at law;
  • the agreement can be proven through clear and satisfactory evidence; and
  • the agreement included a clear term preventing either party from unilaterally revoking the wills.

Because mutual wills significantly restrict a person’s testamentary freedom, courts need compelling evidence that a will is truly mutual in nature.

Binding Contract vs. Moral Obligation

One of the central legal issues in mutual wills litigation is distinguishing between a legally binding contract and what the courts describe as an “honourable engagement.”

Many spouses intend to follow a shared estate plan out of trust or moral commitment. However, unless there is evidence of an enforceable agreement not to revoke the wills, the survivor generally remains free to change their estate plan at any time.

The British Columbia Court of Appeal confirmed in Brynelsen v. Verdeck, 2002 BCCA 187, that mirror wills alone are insufficient to establish a mutual wills agreement. There must be separate and independent evidence of an agreement not to revoke.

Similarly, in Fleischer v. Zoltan Elemer Fleischer Alter Ego Trust, 2024 BCSC 2162, the Court emphasized that the agreement must satisfy the ordinary requirements of contract law and include a clear commitment not to revoke the wills. Per Mayer v. Mayer Estate, 2018 BCSC 2225 at para. 139, the evidence must be “clear and unequivocal,” including certainty of terms.

Mutual wills agreements create a significant and continuing obligation on the surviving will-maker. Once the first will-maker dies, the survivor is no longer free to deal with the property governed by the agreement as they otherwise would.

Recent British Columbia Case: Siebert Estate (Re), 2025 BCSC 617

A recent British Columbia decision illustrates the distinction between a joint will and a binding mutual wills agreement.

In Siebert Estate (Re), 2025 BCSC 617, the Court considered a handwritten joint German will executed by spouses in 1995. The will provided that, upon “our death”, the estate would pass to the wife’s parents.

Years later, the wife executed a second handwritten will in British Columbia expressly revoking prior testamentary dispositions and leaving her estate to her husband. The issue before the Court was whether the later will revoked the earlier joint will.

The Court confirmed several important principles regarding mutual wills:

  • a joint or mirror will alone is not enough to establish a binding mutual wills agreement;
  • there must be clear and unequivocal evidence of an agreement not to revoke the wills; and
  • absent such an agreement, either party may revoke or change their will during their lifetime.

The Court also confirmed that a constructive trust will only arise where there is a binding agreement not to revoke and the first party dies without breaching that agreement. In the case before the Court, no constructive trust arose because there was no evidence of a binding agreement and one spouse had already revoked their participation in the joint will before death.

As a result, the later will revoked the earlier joint will and the deceased died intestate under British Columbia law.

Can Mutual Wills Be Revoked?

Mutual wills create a continuing obligation between the will-makers, but the timing of any revocation is critical.

Revocation During Both Parties’ Lifetimes

  • During the joint lives of both parties, a mutual will may generally be revoked unilaterally if the revocation is communicated openly to the other party.

Mutual Revocation

  • A mutual will cannot be revoked without the consent of the other party where the agreement remains operative.

After the First Death

  • Once one party dies having complied with the agreement, the survivor can no longer defeat the arrangement by revoking or altering their will.

What Happens if the Survivor Breaches the Agreement?

Where a surviving will-maker later changes their estate plan in breach of a valid mutual wills agreement, the court may impose a constructive trust over the survivor’s estate for the benefit of those who were intended to inherit under the original arrangement.

Importantly, the mutual wills themselves do not automatically create a trust. Rather, the constructive trust arises because of the survivor’s breach of the underlying agreement.

In Nelson v. Trottier, 2019 ONSC 1657 at para. 47, the Court confirmed that the constructive trust remedy arises from the breach of the mutual wills agreement itself.

Similarly, the Court in Mayer v. Mayer Estate, 2018 BCSC 2225 at para. 144, explained that “authorities establish the existence of mutual wills is by itself not sufficient to establish a trust, but the wills provide some evidence of a common intention and agreement respecting the property in issue”.

Equitable Remedies in Mutual Wills Litigation

Mutual wills disputes frequently involve sophisticated equitable remedies, particularly where assets have been transferred away from the estate.

Where trust assets are improperly transferred to third parties in breach of the mutual wills agreement, beneficiaries may pursue:

  • a proprietary remedy based on the beneficiary’s equitable interest in the transferred property; and
  • a personal remedy based on the doctrine of knowing receipt.

Equitable Tracing

Equitable tracing enables a claimant, typically a beneficiary or equitable owner, to assert a proprietary remedy over property subject to a constructive trust.

If property subject to the constructive trust is transferred out of the estate, the beneficiary may pursue the assets through tracing, even where the original property has been exchanged, transferred, or mixed with other assets.

This remedy can become particularly important where estate assets are transferred into joint accounts, corporations, trusts, or real property prior to the survivor’s death.

Knowing Receipt Claims Against Third Parties

In some circumstances, beneficiaries may also pursue claims against third parties who knowingly received property transferred in breach of trust.

To establish knowing receipt, a claimant generally must prove:

  • receipt of trust property for one’s own benefit, rather than merely as an agent; and
  • knowledge or constructive knowledge that the property was transferred in breach of trust or fiduciary duty.

If these elements are established, the recipient may face personal liability.

Why Mutual Wills Litigation Is Complex

Mutual wills disputes can become legally complex because they often involve issues relating to contracts, trusts, estate law, and equitable remedies. These disputes commonly arise in blended families where different beneficiaries are competing over the estate.

The central issue is usually whether the parties made a genuine binding agreement not to change their wills, or whether they simply shared a common intention that was never meant to be legally enforceable.

Because a finding of mutual wills can significantly restrict a person’s ability to change their estate plan, courts approach these claims cautiously and require strong evidence before concluding that a binding mutual wills agreement exists.

If you believe a mutual wills agreement may exist, or if you are involved in a dispute concerning changes to an estate plan after a spouse’s death, obtaining legal advice early is critical.

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