Mutual Wills and Mirror Wills: Understanding the Difference

Mirror wills, mutual wills and joint wills

Mirror wills are two separate wills whose terms correspond. A typical example is a couple who each leave everything to the other, and if the other has died, to their children equally. Each will is a separate instrument, and the fact that the wills match does not prevent either person from changing theirs.

Mutual wills are wills made under an agreement between the will-makers, intended to be legally binding, about how their property will pass and under which each is bound not to revoke or depart from the agreed will. The wills are often in mirror form, but they need not be. It is the agreement, not the similarity of the documents, that makes them mutual.

A joint will is a single document signed by two people as the will of each. Joint wills are rarely used. A joint will is not mutual unless the same kind of binding agreement is proved.

What must be proved

The leading Australian case is the High Court’s decision in Birmingham v Renfrew (1937) 57 CLR 666, an appeal from Victoria. A husband and wife orally agreed that she would leave her property to him and that, in return, he would make a will leaving his property to four of her relatives and would not revoke it. After she died and he took under her will, he made a new will benefiting others. The Court held that the agreement created a constructive trust that her relatives could enforce against his executors.

In Osborne v Estate of Osborne [2001] VSCA 228, the Victorian Court of Appeal said that equity will not intervene unless it is shown, by clear evidence, that a will-maker bound themselves to an obligation not to revoke their will, in terms that equity can enforce. Whether that obligation is called a contract, an agreement or a promise is a matter of nomenclature. In practice, the person relying on mutual wills must prove:

• an agreement between the will-makers about how their property will pass, under which each is bound not to revoke or depart from the agreed will (the obligation may be express, or inferred from the evidence as a whole);
• that the agreement was intended to create binding obligations, not just a shared plan, hope or moral expectation;
• terms certain enough to be enforced, including which property is covered; and
• that the first to die acted on the agreement, typically by dying with their will unrevoked so that the survivor benefited under it.

The evidence must be clear and satisfactory. In Birmingham, Latham CJ warned that such agreements are easy to allege after the parties have died, and that making corresponding wills, each naturally explained by the other, is not enough by itself to establish a binding agreement not to revoke. In Osborne, the Court of Appeal upheld a finding that no such agreement had been proved, even though the parents had made wills in identical terms on the same day. Useful evidence includes an express written agreement, recitals in the wills, the lawyer’s file notes and instructions, and correspondence.

Does the agreement need to be in writing?

There is no general rule that it must be. The agreement in Birmingham was oral, and land was involved. The High Court nonetheless enforced it, holding that the agreement was not within the writing requirement then found in section 128 of the Instruments Act 1928 (Vic). That decision turned on the legislation of the time and does not mean writing requirements are always irrelevant.

Today, section 53(1) of the Property Law Act 1958 (Vic) requires writing to create or dispose of an interest in land, to prove a declaration of trust of land, and to dispose of an existing equitable interest. Section 53(2) provides that the section does not affect the creation or operation of resulting, implied or constructive trusts. Because the mutual-wills trust is a constructive trust arising by operation of equity, section 53(1) does not of itself defeat it. In practice, though, an oral agreement is very difficult to prove, so anyone intending to make binding mutual wills should record the agreement in a signed written document.

While both parties are alive

The agreement does not remove the statutory power to revoke a will. Under section 12 of the Wills Act 1997 (Vic), a will can be revoked by a later will, by a writing declaring an intention to revoke it and executed like a will, or by destroying it (or certain dealings with it) with that intention, and under section 13 it can also be revoked by marriage. A revocation is effective as a matter of wills law even if it breaches the agreement.

Whether revoking during the parties’ joint lives is a breach, and what notice is required, depends on the agreement. In Birmingham, Dixon J considered that the contract bound the husband, during his wife’s lifetime, not to revoke his will without notice to her, and that if she died without altering her will he was bound not to revoke his at all. He observed that such an agreement assumes neither party will alter their will without the other’s knowledge. Notice matters because it gives the other party the chance to reconsider their own will while they still can. The consequences where the first to die secretly revoked their will before dying are not settled by Birmingham; in Barns v Barns [2003] HCA 9, Gummow and Hayne JJ noted that Dixon J’s principles were not directed to that situation. A well-drafted agreement states whether, and how, either party may withdraw while both are alive, for example by written notice to the other.

After the first death: the constructive trust

Once the first party has died having kept to the agreement, the survivor can still make a new will, and that later will is valid and can be admitted to probate. As Dixon J explained in Birmingham, however, equity attaches the obligation to the property: the survivor becomes a constructive trustee, and the terms of the trust are those of the will the survivor promised would be their last will. The obligation rests on the survivor having taken the benefit of the first party’s will, made in reliance on the agreement.

Dixon J also recognised that the purpose of such an arrangement is often to let the survivor deal with the property as owner during their lifetime, including by converting it and spending the proceeds. He described a “floating obligation”, suspended during the survivor’s lifetime, which descends on the assets at the survivor’s death and crystallises into a trust, and said the survivor could not make gifts or settlements during their lifetime calculated to defeat the agreement. The exact scope of what the survivor can and cannot do depends on the terms of the agreement.

What property is affected

Not every asset the survivor holds is automatically caught. The answer depends on the agreement’s terms, and it helps to separate the following categories:

• Property the agreement covers. The starting point is what the parties actually agreed. An agreement may be confined to particular assets, or may extend to all property each party owns at death, as the deed in Barns did.
• Property received from the first to die. In the High Court’s analysis in Birmingham, as summarised in Barns, the subject matter of the obligation is the property passing to the survivor under the first will, identified once that estate has been administered.
• The survivor’s own and later-acquired property. This is caught only if the agreement, on its proper construction, extends to it. If the wills or agreement are silent, this is a common source of dispute.
• The position during the survivor’s lifetime. Until the survivor dies, the obligation is usually a floating one rather than a fixed trust over particular assets. The survivor may generally use, sell and spend the property as the agreement permits.
• Lifetime gifts and transfers. Ordinary consumption and genuine dealings are usually permitted, but voluntary gifts or settlements calculated to defeat the agreement are not. The line depends on the terms and the facts.
• Jointly owned property and superannuation. Jointly owned property generally passes to the surviving joint owner by survivorship, and superannuation is paid by the fund trustee under the fund’s rules, to a dependant or to the estate. Neither passes under the will, so each is affected only if, and to the extent that, the agreement and the facts extend to it. See our guides to superannuation and your will and binding death benefit nominations.

Who can enforce it and what remedies are available

The beneficiaries intended by the agreement can enforce the constructive trust against the survivor’s executors after the survivor dies. In Birmingham, the High Court held that the wife’s relatives could do so, and left it to the Supreme Court of Victoria to settle the terms of the trust binding the executors.

Rights during the survivor’s lifetime are more limited and depend on the agreement. In Thynne v Sheringham [2023] NSWCA 181, the New South Wales Court of Appeal considered an agreement, recorded in a signed memorandum of wishes, that a widow would leave a property or the remaining proceeds of its sale to her late husband’s sons. Because she was entitled to sell the property and use the proceeds for her own needs, the Court held that one son did not have a caveatable interest in the land; the obligation was a floating one. The decision is persuasive, not binding, in Victoria, and turned on that agreement. A beneficiary who is concerned that a survivor is giving property away to defeat an agreement should get advice promptly.

Later wills, marriage and divorce

Under section 13 of the Wills Act 1997 (Vic), a will is revoked by the will-maker’s marriage. That does not revoke a gift to, or appointment of, the person the will-maker is married to at death, or certain powers of appointment, and it does not revoke a will made in contemplation of that marriage or expressed to be made in contemplation of marriage generally.

Under section 14, divorce revokes a gift to the former spouse, certain powers of appointment, and the former spouse’s appointment as executor, trustee or guardian (except as trustee of property left on trust for beneficiaries who include the former spouse’s children), unless it appears the will-maker did not want that to happen. The will then takes effect as if the former spouse had died first. Sections 13 and 14 are expressed in terms of marriage and divorce.

These rules affect the will itself. Because, on the reasoning in Birmingham, the equity attaches to the property rather than to the will, revocation of the survivor’s will does not by itself decide whether the survivor remains bound by the agreement. An agreement should say expressly what happens if either party remarries, separates or divorces.

Family provision claims

Mutual wills do not exclude family provision claims. Under section 91 of the Administration and Probate Act 1958 (Vic), the Court may order provision out of a deceased person’s estate for the proper maintenance and support of an eligible person, and nothing in a private agreement removes that power.

In Barns v Barns [2003] HCA 9; (2003) 214 CLR 169, a husband, wife and son signed a deed and the spouses made wills under it. The husband died first, leaving everything to his widow. The High Court, applying the South Australian family provision Act, declared that the deed did not prevent an application by his daughter (and her children) for provision out of his estate. The case supports the proposition that a private mutual-wills arrangement cannot oust family provision jurisdiction. It concerned South Australian legislation and the first estate, so it does not decide what property forms part of a Victorian deceased estate, or how a particular constructive trust affects the estate available under section 91. Those questions depend on the agreement, the facts and the Victorian Act. Our guide to family provision claims in Victoria explains who is eligible and how claims are decided.

Practical risks of mutual wills

Mutual wills can provide certainty for children, particularly in blended families, but they also create risks:

• they can tie the survivor to decisions made many years earlier, even if circumstances change significantly;
• disputes often arise because the agreement was not written down or its terms were unclear;
• the survivor’s freedom to sell, spend or give away property is often uncertain unless the agreement deals with it; and
• family provision claims, remarriage and assets outside the estate can still change the outcome.

A couple who want binding wills should have a separate written agreement that states the obligation not to revoke or depart from the agreed wills, which property is covered (including each party’s own and later-acquired property), what the survivor may do with it during their lifetime, how either party may withdraw while both are alive, and what happens on remarriage or separation. Each party should consider getting independent advice. See also our guide to estate planning for blended families.

Alternatives to mutual wills

The same objectives can often be met in more flexible ways:

• Testamentary trusts, which can hold assets for the survivor and children under terms set by the will; see our article on testamentary trusts.
• A life interest or right to reside, giving the survivor the use of the home or income for life, with the capital passing to children afterwards.
• Holding property as tenants in common, so that each owner’s share passes under their own will rather than to the survivor automatically.
• Superannuation death benefit nominations, made in accordance with the fund’s rules.

Each option has different tax, flexibility and family provision consequences, and the right choice depends on the family and the assets.

Primary Sources

• Wills Act 1997 (Vic) — ss 12, 13 and 14
• Property Law Act 1958 (Vic) — s 53
• Administration and Probate Act 1958 (Vic) — Part IV, s 91
• Birmingham v Renfrew (1937) 57 CLR 666; [1937] HCA 52
• Osborne v Estate of Osborne [2001] VSCA 228
• Barns v Barns (2003) 214 CLR 169; [2003] HCA 9
• Thynne v Sheringham [2023] NSWCA 181 (New South Wales; persuasive only)

Related reading

Our article on why every Victorian adult needs a will sets out the broader case for proper estate planning, and our guide to probate in Victoria explains how the Court oversees the administration of estates where disputes arise.

Frequently Asked Questions