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Testamentary Capacity

Also known as: Sound Mind, Mental Capacity, Competence to Make Will

Definition

Testamentary capacity is the legal requirement that you understand the nature of making a will, know what you own, recognise who should reasonably benefit, and are not influenced by any mental disorder when making your will.

Having testamentary capacity is essential for making a valid will. Without it, your will can be declared invalid, meaning your estate would be distributed under intestacy rules rather than according to your wishes.

What Does Testamentary Capacity Mean?

Testamentary capacity is governed by case law, not statute. The test comes from Banks v Goodfellow (1870), which established four requirements that remain the definitive standard today. The case was recently confirmed in Walker v Badmin (2015), which clarified that the Mental Capacity Act 2005 does not apply to testamentary capacity, and most recently in Leonard v Leonard (2024), where the court stated the Banks test has "stood the test of time." All four requirements must be satisfied for a will to be valid.

Under Banks v Goodfellow, the testator (the person making the will) must: (1) understand the nature of making a will and its effects—meaning they comprehend they're making a legally binding document that will distribute their property after death, (2) understand the extent of the property they're disposing—they must have a general understanding of what they own, though not necessarily exact values, (3) comprehend and appreciate the claims to which they ought to give effect—they must understand who has reasonable claims on their estate, such as spouse, children, or dependents, and the moral obligations they have toward them, and (4) have no disorder of the mind that perverts their sense of right or prevents the exercise of their natural faculties—no mental illness, delusion, or disorder should distort their judgment about disposing of property. The threshold is deliberately set low to allow elderly people to make wills during their declining years.

Critically, capacity is assessed at the specific moment of will execution, not generally. A dementia diagnosis does not automatically mean you lack testamentary capacity. Many people with early or moderate dementia retain capacity, especially on "good days" when they're alert and clear-thinking. Capacity can fluctuate due to time of day, medication, physical health, stress, or illness. Margaret, 79, has early-stage Alzheimer's. On a Tuesday morning when she's rested and alert, she meets with her solicitor. She clearly explains she wants her £300,000 estate split equally between her three children, understands what she owns, and recognises her children's claims. She has testamentary capacity at this moment, even though she might not have it later that week. The "golden rule"—a judicial recommendation, not a legal requirement—states that when a testator is elderly or seriously ill, a solicitor should arrange for a medical professional to assess capacity and ideally witness the will. While not mandatory, this provides strong evidence to defend the will if challenged later.

There's a legal presumption of capacity—the law assumes people have capacity unless proven otherwise. If a will appears rational and properly executed, capacity is presumed. The burden of proof falls on anyone challenging the will to prove the testator lacked capacity. However, if suspicious circumstances exist (such as the testator having known mental illness, the will making inexplicable dispositions, or a beneficiary being involved in preparation), the burden may shift. Professional will preparation significantly strengthens the presumption of capacity, as courts trust that experienced solicitors wouldn't prepare a will for someone lacking capacity. Medical evidence at or near the time of execution is most valuable for defending or challenging a will. Retrospective capacity assessments are difficult but possible using medical records, witness statements, and contemporaneous file notes from the solicitor who prepared the will.

Testamentary capacity differs from undue influence—capacity concerns the testator's mental state, while undue influence involves external pressure or coercion. Both can invalidate a will, but they're separate legal tests often confused by those unfamiliar with will law. If capacity is permanently lost, the Court of Protection can authorise a "statutory will" under the Mental Capacity Act 2005, made in the person's best interests—this is the only context where the MCA applies to wills.

Common Questions

"Can someone with dementia make a valid will?" Yes, a dementia diagnosis doesn't automatically prevent someone from making a valid will. What matters is whether they have testamentary capacity at the specific moment they sign—meaning they understand they're making a will, know roughly what they own, recognise who should inherit, and aren't affected by delusions. Many people with early or moderate dementia retain this capacity. It's strongly recommended to have a medical professional assess capacity and witness the will.

"What happens if someone made a will when they didn't have mental capacity?" If proven that the testator lacked testamentary capacity when making their will, the will is invalid and cannot be admitted to probate. The estate would then be distributed according to an earlier valid will (if one exists) or under intestacy rules. Anyone with a financial interest can challenge on capacity grounds, but they must prove lack of capacity—there's a legal presumption that people have capacity unless evidence shows otherwise.

"How is testamentary capacity assessed when someone makes a will?" A solicitor should ask questions to check the testator understands: (1) they're making a will and what that means, (2) roughly what property they own, (3) who has reasonable claims on their estate, and (4) they're not influenced by delusions. If the testator is elderly or ill, the "golden rule" recommends involving a medical professional (GP or psychiatrist) to assess capacity and ideally witness the will, providing a written assessment against the four Banks v Goodfellow requirements.

Common Misconceptions

Myth: If you have dementia or Alzheimer's, you automatically can't make a valid will.

Reality: A diagnosis of dementia, Alzheimer's, or any mental illness does not automatically mean you lack testamentary capacity. Capacity is assessed at the specific moment you make your will, and many people with cognitive decline still have periods of lucidity when they understand what they're doing. The law deliberately sets a relatively low threshold for testamentary capacity to allow older people to make wills during their declining years. What matters is whether you meet the four requirements of the Banks v Goodfellow test at the time you sign your will.

Myth: The Mental Capacity Act 2005 sets the standard for whether you can make a will.

Reality: The Mental Capacity Act 2005 does not apply to testamentary capacity for wills. The test remains the common law standard from Banks v Goodfellow (1870), definitively confirmed by courts in Walker v Badmin (2015) and Leonard v Leonard (2024). The MCA test can be used as a "cross-check" but is not determinative. The only exception is statutory wills—if someone completely lacks capacity, the Court of Protection can authorise a will under the MCA, but that's a different process entirely from making your own will.

Understanding testamentary capacity connects to these related concepts:

  • Banks v Goodfellow Test: The specific legal test defining testamentary capacity through four requirements established in 1870 case law.
  • Testator: The person making the will whose testamentary capacity must be assessed.
  • Undue Influence: A separate ground for will invalidity involving external pressure rather than the testator's mental state.
  • Capacity Assessment: The practical process used to determine whether testamentary capacity exists, particularly under the golden rule.
  • Mental Capacity Act 2005: The statutory framework that governs most capacity decisions but explicitly does not apply to testamentary capacity for wills.

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Legal Disclaimer: This glossary entry provides general information about UK legal terminology and does not constitute legal advice. Testamentary capacity is a complex legal issue with significant consequences. For advice specific to your situation, consult a qualified solicitor specialising in wills and estate planning.