In estate planning, trends tend to move slowly. But over the past few years, Mutual Will Agreements have experienced a quiet revival — particularly after a significant decision in 2024 of the Supreme Court of Victoria, which confirmed that mutual will agreements can create a constructive trust over a surviving spouse’s estate.
That matters.
Because it may limit the ability of third parties to bring a successful family provision claim — and it may prevent assets being diverted away from the children the couple originally intended to benefit.
So what exactly are Mutual Wills?
And when are they appropriate?
What Is a Mutual Will Agreement?
A Mutual Will Agreement is more than just two spouses making similar Wills.
It involves:
- Each person making a Will in agreed terms; and
- A binding agreement that neither of them will revoke or change their Will after the first death.
After the first spouse dies, the survivor is legally bound by the agreement.
Even if the surviving spouse later makes a new Will, equity may impose a constructive trust requiring the estate to be distributed in accordance with the original mutual agreement. In simple terms:
The survivor can use the assets during their lifetime,
but they cannot ultimately redirect them away from the agreed beneficiaries.
Why Are Mutual Wills Becoming Popular Again?
- Protection in Blended Families
Blended families are increasingly common.
A typical scenario:
- Husband and wife each have children from prior relationships.
- They want the survivor to be financially secure.
- They ultimately want their respective children to inherit.
Without a Mutual Will Agreement, this can unravel. After the first death, the surviving spouse could:
- Change their Will,
- Leave everything to their own children only,
- Or benefit a new partner.
A Mutual Will Agreement significantly reduces that risk.
It creates enforceable obligations that protect the deceased spouse’s children.
- Preventing Asset Diversion to a New Spouse
Another modern concern is re-partnering. It is not uncommon for a surviving spouse to:
- Remarry,
- Add a new partner to the title of the home,
- Or transfer substantial assets into joint names.
Once assets are transferred into joint tenancy, they may pass automatically to the new spouse by survivorship — completely outside the Will.
A properly structured Mutual Will Agreement can:
- Restrict this behaviour; and
- Require the survivor (or their estate) to account for assets dealt with inconsistently with the agreement.
It does not freeze the survivor’s life — but it prevents them from rewriting history.
- Impact on Family Provision Claims
Family provision claims are claims brought by eligible persons who believe they have not been adequately provided for in a Will.
The recent Victorian decision recognised that where a Mutual Will Agreement creates a constructive trust, the surviving spouse may hold certain assets subject to that trust.
That can mean:
- Those assets are not freely available to satisfy a later family provision claim; or
- The court must recognise the equitable obligations owed to the original beneficiaries.
While each case depends on its facts, this has made Mutual Wills an attractive planning tool again — particularly where asset protection and certainty are priorities.
How Are Mutual Wills Different From Mirror Wills?
This distinction is critical.
Mirror Wills:
- Two people make similar Wills.
- Either person can change their Will at any time.
Mutual Wills:
Two people make Wills and enter a binding agreement not to change them after the first death.
The enforceability lies in the agreement — not merely in similarity of documents. Without a properly drafted agreement, you do not have Mutual Wills.
What Are the Risks?
Mutual Will Agreements are not for everyone.
They can:
- Restrict flexibility for the surviving spouse.
- Create complex litigation if poorly drafted.
- Be inappropriate where asset values or family circumstances are likely to change significantly.
They also require careful drafting to ensure:
- The agreement is legally binding,
- The obligations are clear,
- The scope of the constructive trust is defined,
- And the survivor’s ability to use capital during their lifetime is properly addressed.
Done badly, they cause disputes. Done properly, they create certainty.
When Should You Consider a Mutual Will Agreement?
You may wish to explore this option if:
- You are in a blended family and want to protect children from a prior relationship.
- You are concerned about a surviving spouse re-partnering.
- You want to prevent assets being redirected away from agreed beneficiaries.
- Certainty is more important to you than flexibility.
Mutual Wills are a serious legal arrangement — closer to a contract than an ordinary Will. They should only be implemented with full advice and careful drafting.
Final Thoughts
Estate planning is not only about distributing assets.
It is also about protecting intentions.
In an era of blended families, longer lifespans, and second relationships, Mutual Will Agreements provide a powerful — though carefully targeted — tool to preserve the original agreement between spouses.
They are not suitable for everyone.
But in the right circumstances, they can prevent exactly the kind of unintended outcomes that families spend years litigating over.
If you would like to explore whether a Mutual Will Agreement is appropriate for your circumstances, the wills and estates team at SPG Lawyers would be pleased to assist.
