Mental Capacity and Wills UK 2026: The Testamentary Capacity Test Explained
Updated 15 May 2026 · 8 min read · England & Wales
A will is only valid in England and Wales if the person making it (the testator) had testamentary capacity at the moment of execution. This means not merely that they were conscious or coherent, but that they satisfied a specific four-part legal test established in Banks v Goodfellow (1870). Understanding this test matters both for people making a will and for beneficiaries who may wish to challenge one.
The Banks v Goodfellow Test
In Banks v Goodfellow (1870) LR 5 QB 549, the court held that a testator has testamentary capacity if, at the time of making the will, they:
- Understand the nature of making a will and its effects — they know they are creating a document that will distribute their property on death and is revocable during their lifetime
- Understand the extent of the property they are disposing of — a general (not precise) understanding of what they own; the testator does not need to know the exact value of every asset
- Comprehend the claims of those who might reasonably expect to benefit— they know who their relatives and dependants are, even if they choose to exclude them from the will; the testator must be capable of understanding these claims, not necessarily accept them
- Not be suffering from a disorder of the mind that perverts their judgment— active delusions that directly influence the will's contents will invalidate it; a general mental disorder does not if it does not affect the specific testamentary act
All four elements must be satisfied. A testator may fail only the fourth — for example, having a paranoid delusion that a child is trying to kill them and excluding that child on that basis — and the will may be invalid even if the other three elements are met.
The Presumption of Capacity
There is a legal presumption that an adult who executes a will in proper form had testamentary capacity. The person challenging the will must first raise a credible case that capacity was lacking — typically by producing medical evidence or pointing to unusual provisions. Once raised, the burden shifts to those defending the will to prove capacity on the balance of probabilities.
A will that appears rational on its face (even if unexpected) starts with a stronger presumption than one with irrational or inexplicable provisions.
Dementia and Testamentary Capacity
A diagnosis of dementia does not automatically mean someone lacks testamentary capacity. Dementia is a progressive condition — capacity may fluctuate, and a person may have sufficient capacity during a lucid interval even if they generally lack it at other times. The assessment is specific to the moment the will is executed.
In practice, the further dementia has progressed, the harder it becomes to establish capacity. Key principles:
- A contemporaneous medical assessment carries far more weight than retrospective evidence
- The solicitor's file note from the will execution meeting is critical evidence
- Witness evidence from those present at execution is important but may be partial
- Medical records can be subpoenaed in litigation — earlier entries showing capacity are valuable
The Golden Rule
The Golden Rule, from Kenward v Adams (1975) Times, 29 November, confirmed in Re Simpson (1977) 121 Sol Jo 224, is the professional best-practice standard:
“When a solicitor is instructed to prepare a will for an aged testator or one who is seriously ill, it should be the routine practice to arrange for a medical practitioner first to satisfy himself of the capacity and understanding of the testator, and to make a contemporaneous record of his examination and findings.”
Following the Golden Rule does not guarantee the will will be upheld — it is a recommendation, not a legal requirement. But failure to follow it when the circumstances clearly warranted it weakens the position of those defending the will in subsequent litigation.
Knowledge and Approval
Separate from capacity is the requirement that the testator had knowledge and approval of the will's contents — they understood what was in it and approved it as their own. This requirement is usually satisfied automatically where the testator had capacity and the will was read to or by them. It becomes live where:
- The testator was blind, illiterate, or spoke limited English
- The will was prepared by a person who benefits substantially from it (raising suspicion)
- There are suspicious circumstances surrounding execution
In these cases, the proponent of the will must affirmatively prove knowledge and approval (Barry v Butlin (1838) 2 Moo PC 480).
How to Protect a Will Against a Capacity Challenge
Whether you are making a will now or acting as executor or beneficiary under an existing one, the following steps reduce challenge risk:
- Have a GP or specialist assess and record capacity contemporaneously — use a capacity assessment form and retain it with the will file
- Use a solicitor who follows the Golden Rule — they should produce a detailed attendance note recording observations of the testator's mental state at execution
- Make the will as early as possible — a will made before any cognitive decline begins is far harder to challenge
- Ensure the will reflects the testator's known wishes — unexpected provisions invite scrutiny; a letter of wishes explaining the reasoning is helpful
- Choose witnesses carefully — witnesses should be able to give evidence about the testator's state of mind at execution if needed
- Store the file note and assessment with the will — in a sealed envelope if appropriate, to be opened by the executor after death
What Happens If a Will Is Challenged for Lack of Capacity
A challenge is raised by entering a caveat at the Probate Registry (form PA8, £3), which prevents a grant being issued until the dispute is resolved. The challenger then has 14 days to enter a standing search and file a warning. If the matter proceeds, it becomes a probate claim in the Chancery Division — expensive litigation that typically costs £50,000–£200,000+ per side for a contested trial.
Courts strongly encourage mediation before trial. Most capacity disputes settle — sometimes with partial provision to the challenger, sometimes with the will upheld and costs awarded. The outcome depends heavily on the quality of contemporaneous evidence.
Statutory Wills: When Someone Has Already Lost Capacity
If a person lacks capacity and cannot make or change their will, the Court of Protection can make a statutory will on their behalf under s.18 and Schedule 2 of the Mental Capacity Act 2005. The court applies a best-interests test — what the person would have decided if they had capacity. A statutory will requires an application to the Court of Protection, takes months to obtain, and costs £3,000–£10,000+.
This underscores why making a will early — before any capacity concerns arise — is the most important step available.
Frequently Asked Questions
Can someone with dementia make a will in England and Wales?
Yes — a diagnosis of dementia does not automatically prevent someone from making a valid will. Testamentary capacity is assessed at the moment the will is executed, and a person with dementia may have sufficient capacity during a 'lucid interval' even if they lack capacity at other times. The legal test is the four-part Banks v Goodfellow test (1870), not a medical diagnosis. However, because dementia creates a real risk of a future challenge, it is strongly advisable to involve a doctor to assess and record capacity (the Golden Rule) and to have the assessment documented in a contemporaneous file note.
What is the Banks v Goodfellow test for testamentary capacity?
Banks v Goodfellow (1870) LR 5 QB 549 established that a testator must: (1) understand the nature of the act of making a will and its effects — that they are giving their property away on death; (2) understand the extent of the property of which they are disposing — a general, not precise, understanding; (3) comprehend the claims of persons who might reasonably expect to benefit — know who their relatives and dependants are, even if choosing to exclude them; (4) not be suffering from a disorder of the mind that poisons their affections, perverts their sense of right, or prevents the exercise of their natural faculties in disposing of their property — active delusions that directly affect the will's contents will invalidate it. If all four parts are satisfied, the testator has testamentary capacity.
Who has the burden of proof in a testamentary capacity dispute?
The starting presumption is that a testator had capacity when they executed a will that is rational on its face and executed with the proper formalities. The person challenging the will bears the burden of raising a prima facie case that capacity was lacking. Once raised, the burden shifts to those propounding the will to prove that the testator did have capacity on the balance of probabilities. Where the will is irrational on its face, the burden of proving capacity falls on those upholding the will from the outset (Sutton v Sadler (1857)).
What is the Golden Rule in will-making for elderly or ill testators?
The Golden Rule, formulated in Kenward v Adams (1975) and confirmed in Re Simpson (1977), is a best-practice recommendation — not a legal requirement — that when a solicitor prepares a will for an elderly or seriously ill testator, they should arrange for a medical practitioner to assess the testator's capacity and record the assessment before the will is executed. Following the Golden Rule does not guarantee the will will be upheld, but failure to follow it is often highlighted by courts when a challenge arises. The assessment should be documented in a contemporaneous file note, ideally signed by the doctor.
What is the difference between testamentary capacity and undue influence?
Testamentary capacity and undue influence are distinct grounds for challenging a will. Capacity focuses on the testator's mental state — whether they understood what they were doing. Undue influence focuses on external pressure — whether someone overborne the testator's free will and caused them to make a will they would not otherwise have made. A testator can have full capacity and still be unduly influenced (if they are pressured despite understanding). Conversely, a testator may lack capacity without any undue influence. Courts treat them as separate grounds; a claimant may plead both. Undue influence is notoriously difficult to prove because it requires evidence of coercion, not merely persuasion or suggestion.
What is a statutory will and when is one needed?
A statutory will is made by the Court of Protection under the Mental Capacity Act 2005 on behalf of a person (P) who lacks testamentary capacity and cannot make or change their own will. The court applies a best-interests test — what P would have decided if they had capacity, looking at their past wishes, beliefs, values, and relationships. A statutory will can be urgently needed when: P has no existing will and would die intestate leaving assets to the wrong people; P's existing will is outdated and does not reflect their circumstances; the estate is large enough for IHT planning to be worthwhile. The application process takes months and costs £3,000–£10,000+ including court fees and legal costs.
Make Your Will While You Have Capacity
The single most effective way to protect against a capacity challenge is to make your will early — before any cognitive decline begins. Our DIY will kit is designed for people who are fully capable and want to get their affairs in order without delay.
Get the WillSafe Kit →Related Articles
- Testamentary capacity — the Banks v Goodfellow test in detail
- Contesting a will — all grounds explained
- Writing a will when ill or terminally ill
- Statutory wills — when the Court of Protection makes a will
- Undue influence and wills
- LPA and dementia — acting before capacity is lost
- Court of Protection deputyship
This article is for general information only and does not constitute legal advice. Capacity disputes and contested wills require specialist probate solicitor advice.