What is testamentary capacity in UK law?

Testamentary capacity is the legal standard of mental capacity required to make a valid will in England and Wales. It is governed by the common law test established in Banks v Goodfellow (1870). To have testamentary capacity, a person must: understand the nature and effect of making a will; understand the extent of the property they are disposing of; understand the claims of those who might reasonably expect to benefit; and have no disorder of mind that poisons their affections, perverts their sense of right, or prevents the exercise of natural faculties. All four elements must be satisfied at the time of signing.

Does dementia mean someone cannot make a will?

Not automatically. Dementia reduces testamentary capacity but does not automatically eliminate it. Capacity is assessed at the moment the will is made, not generally across the person's life. A person with early-stage dementia may have sufficient capacity on a 'lucid interval' — a period of clarity — to make a valid will. The key is medical evidence that capacity was present at the time of signing. This is why the Golden Rule recommends a medical assessment for elderly testators or those with cognitive conditions.

What is the 'Golden Rule' in will-making?

The Golden Rule (from Kenward v Adams [1975]) states that when a solicitor is instructed to prepare a will for an elderly person or someone whose capacity may be in doubt, the solicitor should arrange for a medical practitioner to assess and record the testator's capacity at the time the will is made. A written capacity assessment at the time of signing is the strongest possible evidence against a later challenge on grounds of lack of capacity.

Is testamentary capacity the same as the Mental Capacity Act test?

No. Testamentary capacity is governed by the common law Banks v Goodfellow test (1870) — not the Mental Capacity Act 2005 (MCA). The MCA test is used for most decisions about personal welfare and property. The Banks test applies specifically to making wills, codicils, and revocations. The MCA test and the Banks test are similar in spirit but technically distinct — a person can satisfy one without the other. Courts have confirmed that the Banks test remains the correct test for wills.

What happens if a will is made without testamentary capacity?

A will made without testamentary capacity is invalid and has no legal effect. The estate passes as if the will had never been made — either under a prior valid will, or (if none) under the intestacy rules. Anyone with a financial interest in the estate can apply to the court to challenge the will on grounds of lack of testamentary capacity. The burden of proof is on the challenger; courts presume capacity if the will appears rational on its face. If no will is valid, beneficiaries may lose out significantly compared to what the deceased intended.

Can someone contest a will on grounds of testamentary capacity in the UK?

Yes. Lack of testamentary capacity is one of the five grounds for contesting a will in England and Wales: (1) lack of testamentary capacity; (2) undue influence; (3) improper execution under s.9 Wills Act 1837; (4) lack of knowledge and approval; (5) fraud or forgery. The challenger must bring proceedings within the limitation period (there is no strict time limit for probate challenges, but delay weakens the claim). If the challenge succeeds, the will is pronounced invalid and the court distributes the estate under the next valid will or intestacy.

How do I protect my will from a capacity challenge?

The best protections are: (1) make your will while clearly of sound mind — do not wait until health deteriorates; (2) use a solicitor, who notes their observations about your capacity and understanding; (3) obtain a medical capacity assessment and have a doctor sign a witness statement at the time of signing if there is any doubt about capacity; (4) write a letter of wishes explaining the reasoning behind your decisions — this can rebut claims that the will does not reflect genuine intentions; (5) ensure proper execution under s.9 Wills Act 1837 (signed, witnessed by two independent adults present at the same time).

Testamentary Capacity UK: What It Is, the Banks v Goodfellow Test & How to Protect Your Will

What is testamentary capacity?

Testamentary capacity is the legal threshold of mental capacity required to make a valid will in England and Wales. A will made without testamentary capacity is void — it has no legal effect and the estate passes under a prior will or the intestacy rules as if the invalid will had never been made.

The governing test was established over 150 years ago in Banks v Goodfellow (1870) LR 5 QB 549, and remains the correct legal standard for will-making today, confirmed by the Supreme Court in Walker v Badmin (2015) and subsequent cases. Crucially, it is not the same as the Mental Capacity Act 2005 test used for most healthcare and financial decisions.

The Banks v Goodfellow test: four requirements

All four elements must be satisfied at the time the will is signed:

Understands the nature and effect of making a will

The testator must know that they are making a will, that it takes effect on death, that it can be revoked before death, and that it is separate from other legal documents. They do not need to understand every legal technicality — a broad understanding is sufficient.

Understands the extent of the property they are disposing of

The testator must have a general understanding of what assets they own — not necessarily exact figures, but a broad sense of the estate. A testator who completely forgets they own a house worth £400,000 may fail this element.

Understands the claims of those who might expect to benefit

The testator must be able to consider the claims of people who might reasonably expect to benefit — typically close family members. They do not have to include them, but they must be capable of considering their claims and making a deliberate choice about whether or how to provide for them.

Has no disorder of mind that poisons the will

The testator must not have a mental disorder that perverts their judgment or distorts their wishes in ways they would not have endorsed if of sound mind. This element focuses on the effect of any disorder — not its mere presence. A person with a diagnosed mental illness can still have testamentary capacity if the illness does not affect their will-making judgment.

Dementia and testamentary capacity

Dementia is the most common reason testamentary capacity is contested, but a diagnosis of dementia does not automatically mean someone lacks testamentary capacity.

Capacity is assessed decision by decision and moment by moment. A person with moderate dementia may have a "lucid interval" — a period of clarity in which they fully satisfy the Banks v Goodfellow test and can make a valid will. The courts have upheld wills made by people with dementia where evidence showed capacity at the moment of signing.

The practical message: make your will early

Once dementia has progressed, proving capacity becomes difficult and expensive — even if capacity technically remains. Making your will while clearly of sound mind, with professional involvement, eliminates the risk entirely.

The Golden Rule: protecting the will from challenge

The Golden Rule (established in Kenward v Adams [1975] CLY 3591) requires that when a solicitor takes instructions for a will from an elderly person, or someone whose capacity may be in doubt, the solicitor should:

Arrange for a medical practitioner who knows the testator to assess capacity before the will is executed
Record that assessment in writing at the time
Have the medical practitioner witness the will if possible

The Golden Rule is not legally mandatory — but a solicitor who fails to follow it when there are obvious signs of cognitive decline risks professional censure, and the absence of a contemporaneous medical record significantly weakens the will's defence against challenge.

For DIY will-makers who have any concerns about capacity — their own or a relative's — arranging a GP letter or specialist assessment at the time of signing is the equivalent protective step.

Testamentary capacity vs other grounds for contesting a will

Ground	What it means	Best defence
Lack of testamentary capacity	Testator did not satisfy the Banks v Goodfellow test at time of signing	GP/specialist capacity assessment at signing; solicitor attendance notes
Undue influence	Testator was coerced or pressured into making the will by another person	Independent taking of instructions; letter of wishes explaining decisions
Improper execution (s.9 Wills Act 1837)	Will not signed correctly or witnesses not both present	Follow s.9 requirements exactly; two independent adult witnesses
Lack of knowledge and approval	Testator did not understand what was in the will they signed	Solicitor reading will aloud to testator; attendance notes confirming understanding
Fraud or forgery	Will is a fake or was obtained by deceiving the testator	Professional drafting; reliable witnesses; solicitor custody

Frequently asked questions

What is testamentary capacity in UK law?: Testamentary capacity is the legal standard of mental capacity required to make a valid will in England and Wales. It is governed by the common law test established in Banks v Goodfellow (1870). To have testamentary capacity, a person must: understand the nature and effect of making a will; understand the extent of the property they are disposing of; understand the claims of those who might reasonably expect to benefit; and have no disorder of mind that poisons their affections, perverts their sense of right, or prevents the exercise of natural faculties. All four elements must be satisfied at the time of signing.
Does dementia mean someone cannot make a will?: Not automatically. Dementia reduces testamentary capacity but does not automatically eliminate it. Capacity is assessed at the moment the will is made, not generally across the person's life. A person with early-stage dementia may have sufficient capacity on a 'lucid interval' — a period of clarity — to make a valid will. The key is medical evidence that capacity was present at the time of signing. This is why the Golden Rule recommends a medical assessment for elderly testators or those with cognitive conditions.
What is the 'Golden Rule' in will-making?: The Golden Rule (from Kenward v Adams [1975]) states that when a solicitor is instructed to prepare a will for an elderly person or someone whose capacity may be in doubt, the solicitor should arrange for a medical practitioner to assess and record the testator's capacity at the time the will is made. A written capacity assessment at the time of signing is the strongest possible evidence against a later challenge on grounds of lack of capacity.
Is testamentary capacity the same as the Mental Capacity Act test?: No. Testamentary capacity is governed by the common law Banks v Goodfellow test (1870) — not the Mental Capacity Act 2005 (MCA). The MCA test is used for most decisions about personal welfare and property. The Banks test applies specifically to making wills, codicils, and revocations. The MCA test and the Banks test are similar in spirit but technically distinct — a person can satisfy one without the other. Courts have confirmed that the Banks test remains the correct test for wills.
What happens if a will is made without testamentary capacity?: A will made without testamentary capacity is invalid and has no legal effect. The estate passes as if the will had never been made — either under a prior valid will, or (if none) under the intestacy rules. Anyone with a financial interest in the estate can apply to the court to challenge the will on grounds of lack of testamentary capacity. The burden of proof is on the challenger; courts presume capacity if the will appears rational on its face. If no will is valid, beneficiaries may lose out significantly compared to what the deceased intended.
Can someone contest a will on grounds of testamentary capacity in the UK?: Yes. Lack of testamentary capacity is one of the five grounds for contesting a will in England and Wales: (1) lack of testamentary capacity; (2) undue influence; (3) improper execution under s.9 Wills Act 1837; (4) lack of knowledge and approval; (5) fraud or forgery. The challenger must bring proceedings within the limitation period (there is no strict time limit for probate challenges, but delay weakens the claim). If the challenge succeeds, the will is pronounced invalid and the court distributes the estate under the next valid will or intestacy.
How do I protect my will from a capacity challenge?: The best protections are: (1) make your will while clearly of sound mind — do not wait until health deteriorates; (2) use a solicitor, who notes their observations about your capacity and understanding; (3) obtain a medical capacity assessment and have a doctor sign a witness statement at the time of signing if there is any doubt about capacity; (4) write a letter of wishes explaining the reasoning behind your decisions — this can rebut claims that the will does not reflect genuine intentions; (5) ensure proper execution under s.9 Wills Act 1837 (signed, witnessed by two independent adults present at the same time).

Make your will now — while capacity is clear

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This article is for general information only and does not constitute legal advice. WillSafe UK is not a firm of solicitors. Laws described apply to England and Wales only. Always consult a qualified solicitor for advice specific to your circumstances.