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A will is invalid for undue influence only if the person who made it was coerced — pressured into a will that was not what they wanted. Persuasion, however strong, is not enough. Unlike lifetime gifts, there is no presumption of undue influence in will cases, so the person alleging it has to prove it, and the Court of Appeal has said it must be more probable than any other explanation. That is a heavy burden, because the one person who knew what happened has died. Closely related but separate grounds are lack of knowledge and approval and fraudulent calumny.
It can be very painful to see a will that seems to reflect someone else's wishes more than those of the person who made it — especially where one relative had become the main carer or controlled day-to-day life towards the end. This page explains what the law means by "undue influence", why it is hard to prove, and how it differs from the related grounds that are often raised alongside it.
This describes the law of England and Wales. Scotland and Northern Ireland have their own rules and courts for disputes about wills.
Undue influence is one of several grounds on which a will can be challenged. For the others, and for how a challenge runs from start to finish, see our guide to contesting a will.
The leading modern statement is the Court of Appeal's judgment in Rea v Rea [2024], given by Lord Justice Newey. It draws on older cases that are still the law.
What is allowed, from Hall v Hall, a 19th-century case: "Persuasion, appeals to the affections or ties of kindred, to a sentiment of gratitude for past services, or pity for future destitution, or the like, — these are all legitimate". A will-maker "may be led but not driven; and his will must be the offspring of his own volition."
What is not: "Pressure of whatever character ... if so exerted as to overpower the volition without convincing the judgment, is a species of restraint under which no valid will can be made."
The test from Wingrove v Wingrove (1885), also quoted in Rea v Rea, is that it is only undue influence when the will-maker "is coerced into doing that which he or she does not desire to do" — when, if they could speak freely, they would say "this is not my wish, but I must do it".
So a relative who asked, nagged, or reminded the will-maker of years of care has not, by that alone, done anything the law treats as undue. The question is whether the will-maker's own wishes were overborne.
In some areas of law the court will presume undue influence from a relationship of trust. That applies to gifts made during a person's lifetime. It does not apply to wills.
As the High Court put it in Re Edwards [2007], quoted in Dunstan v Ball [2024]: "In a case of a testamentary disposition of assets, unlike a lifetime disposition, there is no presumption of undue influence." And in Ugolor v Ugolor [2026]: "In probate proceedings, undue influence must be proved in full without the benefit of presumptions".
This means a close or dependent relationship — an adult child caring for an elderly parent, for example — does not on its own shift anything onto the person who benefited. Rea v Rea itself concerned a daughter who had been her mother's main carer for several years and was left the house. The trial judge found undue influence; the Court of Appeal held the evidence did not support that finding and ordered the will to be admitted to probate.
In practice undue influence is usually argued from circumstantial evidence, because it happens in private and the person it was exercised on has died. That is part of why the burden is described as heavy.
In a court claim, rule 57.7(4) of the Civil Procedure Rules requires anyone who says a will "was obtained by undue influence or fraud" to "set out the contention specifically and give particulars of the facts and matters relied on".
This asks a different question: did the will-maker actually know and approve what the will said? In Gill v Woodall [2010] the Court of Appeal described it as whether the will-maker "did understand what he was doing and its effect". Where there are suspicious circumstances around how a will was made, "it is for those who propound the will to remove such suspicion, and to prove affirmatively that the testator knew and approved".
That is the important contrast. With knowledge and approval, suspicious circumstances can put the burden on the person relying on the will. With undue influence, the burden stays on the person alleging it. The Court of Appeal in Gill v Woodall treated the two as separate questions, and a will can fail for want of knowledge and approval without any finding of undue influence.
This asks whether the will-maker had the mental ability to make a will at all. See our guide on lack of testamentary capacity.
This is where someone poisons the will-maker's mind against a person who would otherwise have benefited, by telling lies about them. Re Edwards, quoted in Dunstan v Ball, describes it as a separate ground, and the person making the accusations must "either know that the aspersions are false or not care whether they are true or false". Honest but mistaken criticism is not fraudulent calumny.
Because the burden is on the person alleging undue influence, cases turn on what can be shown about the will-maker's circumstances and how the will came about. That can include:
None of these proves undue influence on its own. The court weighs them against every other explanation for the will, including that the will-maker simply chose to reward the person who was closest to them.
No official body publishes how often undue influence claims succeed, and this page does not estimate it.
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