It is worth separating the will agreement from what happens to inheritance after a death. Where a family later wants to redirect an inheritance, a deed of variation can sometimes change who benefits within two years of the death, though a mutual will agreement may constrain what the survivor can agree to (gov.uk, change a will after a death, as at July 2026, subject to change). This is another area where advice is commonly taken.
Mutual wills, inheritance tax and thresholds
Mutual wills do not, by themselves, change the inheritance tax position. What matters is the ordinary tax framework: transfers between spouses and civil partners are generally exempt, and unused tax-free thresholds can pass to the survivor. The standard inheritance tax rate is 40%, charged only on the part of an estate above the available thresholds, with a reduced rate of 36% where at least 10% of the net estate is left to charity (gov.uk, inheritance tax, as at July 2026, subject to change).
| Allowance or rate | Level (July 2026) |
|---|
| Nil-rate band (per person) | £325,000 |
| Residence nil-rate band (per person) | Up to £175,000 |
| Combined, married couple or civil partners | Up to £1,000,000 |
| Standard rate | 40% |
| Reduced rate (10%+ to charity) | 36% |
Source: gov.uk/inheritance-tax, as at July 2026. The residence band applies where a home passes to children or grandchildren, and reduces for estates above the £2,000,000 taper threshold. These thresholds are frozen until the end of the 2030-31 tax year (5 April 2031) (gov.uk), subject to change.
One practical point applies to unmarried couples. Because cohabiting partners do not inherit under the intestacy rules that apply where there is no valid will, making wills at all is what secures provision for a partner (Citizens Advice, rules of intestacy, as at July 2026). Whether those wills should be binding is a separate question, and generally one for advice.
Mutual wills in Scotland and Northern Ireland
This guide describes the law of England and Wales. Couples can make wills across the UK, but the surrounding rules differ. Scotland has its own succession law, including legal rights that can entitle a spouse and children to a fixed share of an estate regardless of a will, which affects how a binding arrangement plays out. Northern Ireland has a separate but broadly similar system to England and Wales. Where an estate touches more than one jurisdiction, it can be worth taking advice in each.
Frequently asked questions
What is a mutual will?
A mutual will is one of a pair of wills made under an agreement that neither person will change their will after the first death without consent. Where the wills stay unrevoked at the first death, a constructive trust can arise that binds the survivor to the agreed terms (gov.uk, IHTM12063, as at July 2026). Each person still makes their own valid will.
Are mutual wills legally binding?
They generally can be. HMRC's guidance explains that where mutual wills remain unrevoked at the first death, a constructive trust arises, because it would be fraudulent for the survivor to revoke terms the deceased can no longer change (gov.uk, IHTM12063, as at July 2026, subject to change). The law is complex, so the position is often confirmed with a qualified professional.
What is the difference between mutual wills and mirror wills?
Mirror wills are two matching wills that either partner can change freely, before or after the first death. Mutual wills add a binding agreement not to change, so the survivor can be locked into the agreed terms. Mirror wills favour flexibility; mutual wills favour certainty at the cost of flexibility. Our guide on mirror wills covers the flexible option in more detail.
Can a surviving spouse change a mutual will?
Generally not, once bound. After the first death, the survivor is usually held to the agreed terms, so a later will that departs from them may be enforced against their estate (gov.uk, IHTM12063, as at July 2026). An exception can apply if the first to die had already revoked their own mutual will. This is fact-sensitive and generally discussed with a solicitor.
Can mutual wills be revoked while both people are alive?
Yes, generally. Before the first death the couple can usually revoke or vary the arrangement together by mutual consent, as with any will, using a new will or codicil rather than editing a signed original (gov.uk, make a will, as at July 2026). The binding effect is chiefly a concern once one of them has died. Circumstances vary, so advice is often taken.
Do mutual wills reduce inheritance tax?
Not by themselves. Transfers between spouses and civil partners are generally exempt, and unused thresholds can pass to the survivor, but that reflects the tax rules rather than the mutual agreement. The standard rate is 40% above the available thresholds (gov.uk, inheritance tax, as at July 2026, subject to change). Tax planning is generally discussed with a qualified professional.
Are mutual wills a good idea?
They can suit couples who want firm certainty that an estate reaches agreed beneficiaries, often in second marriages. The trade-off is that the survivor may be unable to adapt to later changes, and disputes about the agreement can be costly. Many people who consider them look at a trust as a more flexible alternative, which is worth discussing with a qualified professional.
About Fairchild Oldfield
The Fairchild Oldfield team brings together estate planning, tax, independent financial advice and client care, working with families across England and Wales.
Fairchild Oldfield are estate planning specialists and will writers, not a firm of solicitors. This article is general information based on practical experience, not legal, tax or financial advice.
Important: This article is general information only and is not legal, tax or financial advice. Reading it does not create a professional relationship. It is based on the law of England and Wales, and other UK jurisdictions may differ. Figures and rules are current as at July 2026 and are subject to change. Before acting, many people choose to seek advice from a suitably qualified professional, such as a solicitor, a STEP practitioner, an accountant, or an FCA-authorised financial adviser, who can consider your individual circumstances.
