Dementia can affect someone’s testamentary capacity, but it does not automatically mean they cannot make or change a will. The question that really matters is whether, at the exact moment the will is signed, the person understood what they were doing, what they own, and who might reasonably expect to benefit.
Even with an Alzheimer’s diagnosis, some people retain that understanding – particularly if the process is planned carefully around their best time of day and explained in the right way.
Key points covered in this post:
- What testamentary capacity means in plain English
- How dementia and cognitive decline can affect decision-making
- The legal tests used in England and Wales (Banks v Goodfellow and the Mental Capacity Act 2005)
- Practical steps families can take if they are worried
- When an independent mental capacity assessment may help
What Is Testamentary Capacity?
Testamentary capacity is the legal and mental ability to make or change a valid will. It is not about whether other people agree with the decisions someone has made. It is about whether the person themselves understood, in broad terms, what they were doing at the time they signed the document.
The legal test comes from a case called Banks v Goodfellow (1870), and it is still used by courts and practitioners today. To have testamentary capacity, a person must be able to:
- Understand that they are making a will and what a will does
- Understand, broadly, what property and assets they are giving away
- Understand who might reasonably expect to benefit from their estate, and weigh those claims
- Make decisions that are not being driven by a disorder of the mind, such as a delusion that distorts how the estate is divided
If any one of these elements is missing, the will may later be challenged as invalid. The estate could then pass under an earlier will, or under the intestacy rules if no valid will exists.
How Dementia Affects Capacity
Dementia is an umbrella term covering conditions such as Alzheimer’s disease and vascular dementia. These conditions affect memory, thinking, and day-to-day functioning over time, and can make it harder to hold information in mind, follow explanations, or plan ahead – all of which matter when making a will.
But a diagnosis alone does not remove someone’s testamentary capacity.
Capacity is decision-specific: a person might lack capacity for complex financial investments but still have enough capacity to make a straightforward will. It is also time-specific: symptoms often fluctuate, so someone may be noticeably clearer in the mornings, or on certain days.
In my experience, I have assessed people with significant cognitive decline who could still articulate, clearly and consistently, what they owned, who mattered to them, and what they wanted to happen after their death. With the right support and timing, they met the Banks v Goodfellow test. That matters enormously for families who are trying to respect someone’s wishes.
The Mental Capacity Act 2005 and Wills
The Mental Capacity Act 2005 (MCA) is the main legal framework for assessing decision-making capacity in England and Wales. It sets out five core principles, including the presumption that a person has capacity unless it is established otherwise, and that people must be supported to make their own decisions wherever possible.
Under sections 2 and 3 of the MCA, a person lacks capacity for a specific decision if, because of an impairment of the mind or brain, they are unable to:
- Understand the relevant information
- Retain it long enough to make the decision
- Use or weigh it as part of the decision-making process
- Communicate their decision by any means
For wills made by the person themselves, the courts have confirmed that Banks v Goodfellow remains the primary legal test for testamentary capacity. The MCA informs good practice around how capacity is assessed and how people are supported, but it does not replace the older case law test for wills.
Where the Court of Protection is asked to approve what is called a statutory will – a will made on behalf of someone who already lacks capacity – the court applies the MCA test and then uses the best interests checklist in section 4 to decide what the will should say. This is a distinct and more complex process, usually led by specialist solicitors.
Practical Signs That Dementia May Be Affecting Capacity
Families often notice changes long before any formal assessment takes place. Signs that dementia may be affecting someone’s ability to make or update a will can include:
- Struggling to recall significant assets, such as a property or savings
- Confusion about close relatives, or sudden unexplained shifts in who they trust or want to benefit
- Strong, fixed beliefs that are clearly untrue – particularly if those beliefs are driving big changes in how the estate is divided (for example, insisting without any evidence that a close family member has “stolen everything”)
- Being unable to follow a simple explanation of what a will does, even with time and repetition
On the other hand, someone with dementia who can describe broadly what they own, who matters to them, and what a will is for may still have testamentary capacity – especially given time, clear explanations, and the right environment.
What Families Can Do If They Are Worried
Encourage early planning
If someone has recently been diagnosed with dementia and is still relatively well, it is worth reviewing the will and considering Lasting Powers of Attorney (LPA) while capacity is more clearly present. Specialist legal advice from a solicitor experienced in wills and mental capacity is a sensible first step.
Ask the solicitor about a capacity check
Many practitioners follow what is known as the “golden rule” when an older or unwell person is making a will. This means arranging a contemporaneous capacity assessment by a suitable professional to reduce the risk of future disputes. It is particularly relevant where there is a dementia diagnosis, a sudden change to long-held wishes, or the potential for family conflict.
Consider an independent mental capacity assessment
An independent assessor – such as an experienced Mental Capacity Act practitioner – can carry out a structured assessment using both the Banks v Goodfellow criteria and the MCA principles. A clear written report can support the solicitor, provide reassurance to the family, and, if needed, assist the court later on. This does not replace legal advice about the will itself.
If capacity is already lacking
Where a person with dementia no longer has testamentary capacity, it may be possible to apply to the Court of Protection for a statutory will. This is a technical process, usually led by solicitors, and the court will look carefully at the person’s past and present wishes, their values, and the views of those close to them. Families do not have to carry that process alone.
When an Independent Social Worker Can Help
Independent social work input is often most useful where there is a mix of dementia, family tension, and difficult decisions about money, care, or housing. As an independent social worker, I am not employed by the local authority. That means I can spend the time needed with the person and the family, offer an objective view, and produce reports that are designed to hold up to legal scrutiny while still being sensitive to the people involved.
I can:
- Carry out mental capacity assessments focused on specific decisions, including testamentary capacity, in line with the MCA and Banks v Goodfellow
- Provide clear, person-centred evidence about how dementia is affecting day-to-day decision-making, communication, and understanding
- Work alongside solicitors, deputies, and attorneys to support best interests decision-making where the person has already lost capacity
- Help families think through linked issues – such as care planning and safeguarding – so the will sits in the context of the person’s wider life and wellbeing
If you are worried about a loved one’s ability to make or update their will, or if a solicitor has asked for an independent capacity assessment, I am happy to have an initial conversation. Get in touch and we can talk through what is needed.
This post is for general information only and is based on current law and guidance in England and Wales, including the Mental Capacity Act 2005 and case law on testamentary capacity. Individual situations are often complex, so please seek tailored legal advice and, where appropriate, specialist capacity assessment for your specific circumstances.
Questions Families Often Ask About Dementia and Wills
Does a dementia diagnosis automatically mean someone cannot make a will?
No, it does not. A diagnosis of dementia does not automatically remove someone’s testamentary capacity. Capacity is assessed at the specific time the will is made, and a person can still meet the legal test if they are able to understand what a will does, what they own, and who might reasonably expect to benefit. Many people with dementia, particularly in the earlier stages, retain this capacity, especially when assessments are planned around their clearest time of day.
What is the Banks v Goodfellow test and why does it matter?
Banks v Goodfellow (1870) is the long-standing legal case that sets out the test for testamentary capacity in England and Wales. It requires that the person making the will can understand what a will does, know broadly what property they are giving away, recognise who might reasonably expect to benefit, and make decisions that are not driven by a disorder of the mind. Courts still apply this test today, and any challenge to a will’s validity is likely to be measured against it.
Can capacity fluctuate in someone with dementia?
Yes, and this is one of the most important things for families to understand. Dementia does not affect everyone in the same way or at the same pace. A person may be much clearer in the morning than in the afternoon, or on some days compared to others. This is why timing and preparation matter so much when a will is being made or reviewed. A well-planned assessment, carried out when the person is at their best, can make a real difference to the outcome.
What is the golden rule when making a will for an older or unwell person?
The golden rule is a practice recommended for solicitors when a will is being made by someone who is elderly or has a known medical condition. It suggests that a contemporaneous capacity assessment should be carried out by a suitable professional at the time the will is signed, with a written record kept. This reduces the risk of the will being successfully challenged later and provides important protection for the person’s wishes.
What happens if someone with dementia no longer has capacity to make a will?
If a person has lost testamentary capacity, it may be possible to apply to the Court of Protection for what is called a statutory will. This is a will approved by the court on the person’s behalf. The court will look carefully at the person’s past wishes, values, relationships, and best interests before making a decision. It is a technical process that is usually led by specialist solicitors, but independent social workers can also contribute evidence about the person’s circumstances and wellbeing.
Why would a solicitor ask for an independent mental capacity assessment?
Solicitors often request an independent capacity assessment when there is any doubt about whether someone can validly make or change a will. This is particularly common where there is a dementia diagnosis, a sudden change in instructions, or the potential for a family dispute. An independent assessment provides a clear, structured, written record of the person’s capacity at the relevant time, which can protect the will from being challenged and give the family confidence that the process was handled properly.
How is an independent social worker different from a GP when it comes to capacity assessments?
Both can contribute to understanding someone’s capacity, but their roles are different. A GP can provide important medical background and has knowledge of the person’s health history. An independent social worker carries out a structured assessment specifically against the legal tests, including Banks v Goodfellow and the Mental Capacity Act 2005, producing a detailed written report designed to stand up to legal scrutiny. Where a capacity question is likely to be contested, or where a solicitor needs clear, documented evidence, an independent social work assessment is often the more appropriate route.
