Mirror wills are a popular choice for UK couples because they’re simple: each partner makes a similar will, usually leaving everything to the survivor, then on the second death to children or other beneficiaries.
But here’s the part that worries people (often after a family argument starts): yes — a mirror will can be contested. In fact, there are two broad ways wills end up in dispute:
- Challenging the will’s validity (arguing it isn’t legally valid), and
- Making a financial claim against the estate (arguing the will is valid, but it doesn’t make “reasonable financial provision”).
This guide explains the main grounds, who can bring a claim, typical time limits, and the practical steps couples take to reduce the risk of disputes — especially in second marriages and blended families.
Read first (pillar guide):
Mirror Wills Explained: The 2025 Guide for UK Couples Planning Their Legacy
Quick answer: can a mirror will be contested?
Yes. A mirror will can be contested like any other will. Common reasons include:
- The will wasn’t signed and witnessed correctly
- Lack of testamentary capacity (the person didn’t have capacity to make the will)
- Lack of knowledge and approval (they didn’t fully understand/approve what they were signing)
- Undue influence (they were pressured into making it)
- Fraud or forgery
- Financial provision claims under the Inheritance (Provision for Family and Dependants) Act 1975
These are widely recognised grounds for contesting wills in England and Wales.
1) Contesting a will vs making a claim against an estate (important difference)
Option A: “The will is invalid” (a validity challenge)
This is where someone argues the will shouldn’t be followed because it’s not legally effective. If they succeed, an earlier will might apply — or the estate might pass under intestacy rules.
Option B: “The will is valid, but it’s unfair” (a financial provision claim)
This is where someone accepts the will is valid, but asks the court for reasonable financial provision from the estate. These claims commonly arise in blended families and second marriages.
2) The most common grounds for challenging a will (validity challenges)
Lack of valid execution (signing/witnessing mistakes)
If the will wasn’t executed correctly, it may be invalid. In practice, problems often appear with DIY wills, last-minute signing, or informal “witnessing” that doesn’t follow the required rules. :contentReference[oaicite:1]{index=1}
Lack of testamentary capacity
This is a claim that the person did not have the mental capacity required to make a will at the time it was signed. Capacity disputes are more common where the will was made late in life, around illness, or after a sudden change of beneficiary.
Lack of knowledge and approval
This is an argument that the person didn’t understand or approve the will’s contents — for example, if the will was prepared quickly, changed significantly, or signed when the person was confused or unwell.
Undue influence
This is where someone claims the will reflects pressure or coercion rather than the person’s true wishes. It can be difficult to prove, but it’s a common allegation in family disputes.
Fraud or forgery
Less common, but it happens — for example, where a signature is forged or a will is fabricated.
3) The “big one” for families: financial claims under the Inheritance Act 1975
Even if the will is valid, certain people can apply to the court for financial provision from an estate under the Inheritance (Provision for Family and Dependants) Act 1975.
Why this matters for mirror wills: mirror wills often leave everything to the survivor. If relationships are strained, or the survivor later changes their will, people who expected to inherit may look at an Inheritance Act claim when the estate is eventually administered.
Time limit (the part people miss)
Inheritance Act claims generally need to be issued within six months from the date of the grant of probate (or letters of administration), although the court can sometimes allow late claims in certain circumstances.
Can stepchildren claim?
Stepchildren aren’t automatically entitled under intestacy, but in some situations a stepchild may be able to bring a claim if they were treated as a “child of the family” and meet the relevant criteria.
4) Why mirror wills can become a “dispute trigger”
Mirror wills are usually not binding. After the first death, the surviving partner can typically make a new will (unless a different legal structure applies).
Disputes often start because family members assume the mirror wills are a permanent “deal”, when legally they’re two separate wills.
These situations frequently increase risk:
- Second marriages / blended families (competing expectations between spouse and children)
- Unequal contributions to the home (deposit, mortgage, renovations)
- Late-life will changes (new partner, carer involvement, isolation)
- Marriage after making a will (marriage can revoke a will unless made in contemplation of marriage)
On that last point: in England and Wales, marriage is still generally treated as revoking an existing will, unless it was made in contemplation of that marriage.
5) How couples reduce the risk of disputes (practical steps that actually help)
1) Get the home ownership right (this prevents a lot of “surprise outcomes”)
If you own your home as joint tenants, it will usually pass automatically to the survivor, outside the will. If you own as tenants in common, your share can usually pass under your will (and can be directed into trust).
Read:
Joint Tenants vs Tenants in Common UK: Key Differences
How to Sever a Joint Tenancy in the UK (Change to Tenants in Common)
2) Use clear, professional drafting (especially if your situation isn’t simple)
The biggest dispute magnet is ambiguity: unclear gifts, missing “what if” clauses, outdated executors, or home ownership not matching the will’s intent.
Related:
Will Writing Services – how to choose the right provider
3) Consider trust planning where it fits (common in blended families)
If your priority is “protect the survivor” and “protect the children’s eventual inheritance”, certain trust structures can help (when drafted correctly). This can reduce the chance of later will changes creating a different outcome than you intended.
Internal links:
Trust and Trustee Services
Specialist Probate Trust
4) Add a short letter of wishes (simple, underrated, very human)
A letter of wishes isn’t usually legally binding like a will, but it can explain the “why” behind your decisions. In real disputes, that human context can lower heat and reduce the chance of a challenge being pursued out of anger or misunderstanding.
5) Keep your wills updated after life changes
Most will disputes have a “this hasn’t been updated in years” backstory.
Read:
Updating Mirror Wills After Major Life Changes
FAQs
Can children contest a mirror will in the UK?
Children can potentially challenge a will’s validity on recognised grounds, and in some cases may bring a financial claim for reasonable provision (depending on circumstances). Each case turns on its facts.
Can the surviving spouse change a mirror will after the first death?
In most situations, yes — mirror wills are separate wills and the survivor can usually change their own will later (unless a different legal structure applies).
How long do you have to contest a will in the UK?
It depends on the type of claim. Inheritance Act claims are generally brought within six months from the grant of probate, although the court can sometimes allow late claims.
Can a stepchild claim against an estate?
Not automatically, but a stepchild may be able to bring a claim in certain circumstances (for example, where they were treated as a child of the family).
Next step
If you’re making mirror wills and you want to reduce the risk of later disputes, the best approach is to make sure the whole plan aligns:
- your wills (clear drafting and up-to-date provisions)
- your property ownership (joint tenants vs tenants in common)
- your wider protection planning (LPAs, trustees, probate practicality)
Helpful starting points:
Mirror Wills Explained (pillar guide)
What Happens to a Mirror Will When One Person Dies?
Probate Services
Disclaimer: This article is general information, not legal advice. Will disputes and Inheritance Act claims are fact-specific. If you’re concerned about your will being challenged (or you’re considering a claim), get tailored advice early.