What mirror wills are
Mirror wills are two separate wills -- one for each partner -- that contain matching provisions. Typically, each partner leaves their entire estate to the other, and then both wills specify the same secondary beneficiaries (usually children) and the same executors. The "mirroring" refers to the symmetry of the provisions, not any legal link between the documents.
Each will is a legally independent document. Either partner can amend or revoke their will at any time without the other's knowledge or consent. This is both the strength and the perceived weakness of mirror wills: they give each partner full autonomy, which also means either can change their mind.
Mirror wills are the most common form of estate planning for married couples and civil partners in England and Wales. They are straightforward to draft, cost-effective (a pair typically costs £250-£550), and appropriate for most straightforward couples with aligned interests.
Mirror wills versus joint wills -- a critical distinction
A joint will is a single document signed by both partners, which is legally binding on both. In theory, this prevents either partner from changing the provisions after the first death. In practice, joint wills are almost never recommended by English law practitioners, for two reasons.
First, the law is unclear. English courts have held in various cases that a joint will may or may not be mutually binding -- the position depends on whether a "mutual wills doctrine" can be established, which requires proof of an agreement not to revoke. This uncertainty creates litigation risk rather than protection.
Second, even if the survivor is bound by the joint will, the restriction is inequitable. If your spouse dies and leaves everything to you, your circumstances may change significantly -- you may need to sell assets, support dependents, or face unexpected care costs. Being irrevocably bound to provisions agreed before those changes is rarely in anyone's best interests.
The mutual wills doctrine, which achieves a similar outcome to a joint will by treating the surviving partner as a constructive trustee, is technically available -- but courts are reluctant to find a binding agreement without very clear evidence. Any couple who want to protect their estate from changes after the first death should consider a life interest trust within their wills rather than a joint will.
Legal note: The mutual wills doctrine derives from equity and has been considered in cases including Re Goodchild [1997] 1 WLR 1216 and Olins v Walters [2008] EWCA Civ 782. The courts require clear and satisfactory evidence of an agreement not to revoke before imposing a constructive trust on the survivor.
The second marriage problem
The most significant risk with straightforward mirror wills arises when one partner remarries after the first death. If partner A dies and leaves everything to partner B, and partner B subsequently remarries, the new marriage automatically revokes partner B's existing will under s.18 of the Wills Act 1837. If partner B dies without making a new will, the estate passes under intestacy -- potentially to the new spouse rather than the children from the original relationship.
Even if partner B makes a new will after remarrying, they are free to leave the inherited estate (including assets that originally belonged to partner A) to the new spouse or anyone else. The children from the original relationship have no automatic protection.
This is not a theoretical risk. In London, where estate values are high and longevity is increasing, the gap between the first and second death is often 20 or more years. A lot can change. The solution is to include a life interest trust in the will for the survivor -- the survivor can use and benefit from the estate during their lifetime, but the capital passes to the agreed beneficiaries on the second death. This is covered in our trust planning guide.
Tip: If you have children from a previous relationship, or if your partner does, straightforward mirror wills may not adequately protect their inheritance. Ask your will writer about a life interest trust provision.
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Mirror wills for unmarried couples
Mirror wills are equally important -- arguably more important -- for unmarried couples than for married ones. Married partners at least receive the statutory legacy of £322,000 under the intestacy rules. An unmarried partner receives nothing. Mirror wills are the only mechanism that ensures each partner inherits from the other.
For cohabiting couples in London, mirror wills should be combined with a review of property ownership. Property held as joint tenants passes automatically on the first death regardless of the will; property held as tenants in common does not. Our guide to wills for unmarried couples covers this in full.
When mirror wills need to change
Marriage revokes existing wills. If you are making mirror wills in contemplation of marriage, they should be expressed as "wills made in contemplation of marriage to [name]" to survive the marriage under s.18(3) of the Wills Act 1837. Otherwise, the marriage will automatically revoke both documents.
The arrival of children is another common trigger for review. A mirror will that leaves everything to the surviving partner with no secondary provision for children is adequate while both partners are alive -- but creates vulnerability if both die in the same accident. Mirror wills for couples with children should include a clear secondary distribution to the children and a guardian appointment.
Separation or divorce is the most important trigger. Divorce removes an ex-spouse as beneficiary and executor under s.18A of the Wills Act 1837, but the will is not revoked. This means a divorced person who has not updated their will may die intestate in effect -- the former spouse cannot inherit, but the existing provisions for them are void, and there is no valid substitute.
Legal note: S.18(3) of the Wills Act 1837 (inserted by the Law Reform (Succession) Act 1995) provides that a will expressed to be made in contemplation of a marriage to a specified person is not revoked by the solemnisation of that marriage. The provision is strict -- the marriage must be to the named person.
Mirror Wills for Couples -- Everything You Need to Know -- common questions
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