Beware of mirror willsClients think they’re fine — advisors need to know that they can lead to unintended consequences

• By: Michael Kulbak

• September 15, 2025

• 09:24

skynesher/iStock

Mirror wills are a common phenomenon across Canada. Couples sign these nearly identical estate documents, leaving everything to one another. After the death of the surviving spouse, assets go to the children and/or other agreed-upon beneficiaries.

Most couples believe they are being responsible when they sign these. It’s a simple approach that checks a bothersome item off of their to-do list, opting for the simplest solution without fully considering the potential consequences.

But while mirror wills are often the easiest planning approach, they’re not always the best. They create an illusion of certainty without any of the enforceable protections you’d get from individual wills, trusts or properly structured beneficiary provisions.

Advisors should watch for these. Things can get messy if a surviving spouse remarries, enters into a common-law relationship, falls victim to undue influence or a romance scam or changes their intentions. The risk is real: mirror wills can lead to unintended disinheritance, tax inefficiencies and tense family conflict.

For example

Jake and Suzy (not their real names) have been together and married for over 18 years. It’s a second marriage for both.

They signed and executed mirror wills together. Each left their entire estate to the other with the provision that upon the death of the surviving spouse, the estate would be passed on to their three children. Jake has two children from a previous marriage; Suzy has one child from a previous marriage.

Jake died and left the matrimonial home, RRIFs and non-registered joint investment accounts to Suzy. All these assets passed outside the estate. After Jake’s death, Suzy established a common-law relationship with Martin. He moved into the matrimonial home. Eventually, Suzy revised her will and left all of the estate to Martin and her child. Jake’s children were disinherited.

The risks of mirror wills

Jake and Suzy’s case illustrates four risks:

1. The survivor can change their will. Mirror wills look synchronized, but they’re not necessarily binding agreements. The surviving spouse is free to change their will at any time, to exclude children, stepchildren, change beneficiaries or rewrite the estate distribution entirely.

2. Beneficiary designations and joint assets bypass the will. Assets like RRSPs, RRIFs, TFSAs and jointly-owned property often pass outside the will via named beneficiaries or joint tenancy. A surviving spouse may intentionally or unintentionally leave everything to one side of the family and ignore the spirit and intent of the mirror will.

3. Blended family conflicts. In second marriages or blended families, mirror wills may be insufficient unless accompanied by structures like spousal or testamentary trusts. Children from a first marriage risk being completely excluded and disinherited.

4. Tax and liquidity issues. Estate liquidity becomes critical when there are significant registered accounts with non-estate beneficiaries, real estate and/or deemed disposition gains on death creating significant tax liabilities. If the surviving spouse handles these poorly, or if the surviving spouse’s death hasn’t been planned for, taxes can soak up a significant chunk of the estate, making less funds available to beneficiaries.

Mutual wills

To avoid some of the negative attributes of mirror wills, some estate planners and/or people who draft wills may suggest a mutual will. Mutual wills are a special type of estate planning agreement in which the survivor agrees not to revoke or change their will once the other partner dies. Mutual wills are backed by a binding contract. The intent is to ensure that both partners’ agreed-upon distribution plan cannot be changed later. It creates certainty that assets will flow as intended and can help prevent unfair disinheritance.

Sometimes though, mutual wills create as many headaches as they solve. A surviving spouse may need assets to deal with a financial and/or health issue, but the asset is specifically assigned in the mutual will. A child or beneficiary may become disabled and need more support.

Furthermore, tax laws may change. Given the constraints associated with a mutual will, a surviving spouse may be unable to adjust to a new tax planning opportunity. What seemed appropriate at the time of signing can become outdated and problematic later.

Customized, individual estate plans are almost always best.

Mirror wills are a red flag

It’s not enough to note that a client has a will. Delve deeper when any of these conditions are present:

• One or both spouses have children from prior relationships.

• There are significant RRIF, insurance or share holdings, and non-estate beneficiaries.

• There are second marriages, large age differences or beneficiaries who may contest the estate.

• There is jointly owned real estate.

• A client is relying on simple, verbal assurance. (“I trust my spouse to do what we agreed to.”)

These dynamics introduce real fragility into what appears to be a unified plan.

Advisor takeaways

Five things:

• Ask the critical question: If one spouse dies, and the surviving spouse remarries or engages in a common law relationship, how would the estate be handled?

• Review RRIF/TFSAs and joint-ownership assumptions. Make sure they align with written wills.

• Leverage estate planning software and prepare what-if models. Simulate scenarios where the surviving spouse rewrites their will, remarries or provides inter-vivos gifts.

• Consider spousal trusts or testamentary trusts for clients in blended situations.

• Treat life insurance as a planning tool, not just a payout. Use it for fairness across families.

Simplicity is not the same as certainty. Mirror wills are common, but they are not a plan.

Financial advisors often focus on growing and protecting assets but estate distribution is where clients’ life-long wealth gets allocated.

Michael Kulbak, MBA, CPA, CMA, TEP, is principal of Kulbak Trust Solutions in Mississauga, Ont.