What are mirror wills?
Mirror wills are two near-identical wills, usually made by a couple, in which each leaves their estate to the other and then on to the same beneficiaries. They remain separate documents, and either person can change or revoke their own at any time — including after the first death.
Mirror wills are the most common arrangement for married couples and civil partners with straightforward affairs. They are cheap, simple, and adequate where the family structure is stable.
The exposure is what happens after the first death. The survivor is free to make a new will, and if they remarry, their existing will is revoked automatically. Children from a first relationship can be unintentionally disinherited — commonly called sideways disinheritance.
Where that risk matters — second marriages, stepchildren, business assets — a life interest trust in each will achieves the same intention while fixing where the capital ultimately goes.