When you make a Will, you’re doing something deeply personal: deciding who benefits, who takes responsibility, and what happens next. Most of the time, the process is straightforward. But when there’s any hint that your mental capacity could be questioned later—because of age, illness, a diagnosis like dementia, medication, or a recent hospital stay—getting it right matters even more.
This guide explains what “testamentary capacity” actually means in England and Wales, why the old case of Banks v Goodfellow still sits at the centre of the test, and how modern solicitors assess capacity in real life. You’ll also see the practical steps that reduce the risk of a challenge—without turning your Will signing into a stressful event.
If you want help putting a robust Will in place, start here: Wills.
What is testamentary capacity (and why does it matter so much)?
Testamentary capacity is simply the legal ability to make a valid Will.
If someone challenges your Will after you die, one of the first arguments they may try is: “They didn’t have capacity when they signed.” If that challenge succeeds, the Will can be set aside and your estate may be distributed under an earlier Will—or under the intestacy rules if there isn’t one.
That risk isn’t limited to people with a formal diagnosis. Capacity concerns can arise when someone:
- has dementia or memory problems (diagnosed or not)
- has delirium during illness, infection, or hospital admission
- is taking strong medication that affects alertness or understanding
- has had a stroke or brain injury
- has fluctuating “good days and bad days”
- has communication barriers (hearing loss, language, speech difficulties) that were mishandled during the process
A carefully prepared Will doesn’t just record your wishes. It protects them.
For families where planning needs extra care and clarity, you may also find this useful: Family Will Solicitors.
The legal test: what Banks v Goodfellow requires
The leading test for testamentary capacity comes from an 1870 case: Banks v Goodfellow. Even though it’s old, it remains the foundation for deciding whether someone has the capacity to make a Will.
In plain English, the test asks whether, at the time the Will was made, you could:
- Understand you are making a Will and what a Will does
- Understand the general extent of your estate (you don’t need a spreadsheet, but you should grasp what you own in broad terms)
- Understand who might expect to benefit from your estate (often called “the claims of potential beneficiaries”)
- Make a rational decision free from a disorder of the mind that affects the Will (for example, a delusion that directly influences who you leave assets to)
That last point is important. The law doesn’t require you to make a “fair” Will. It requires you to make a Will that reflects your decision—made with understanding—and not driven by a mental condition that distorts that decision.
Capacity is time-specific, decision-specific, and evidence-specific
A common misunderstanding is: “They had dementia, so they couldn’t make a Will.” That’s not how the law works.
Capacity is time-specific
The key question is capacity on the day you gave instructions and/or signed the Will (and ideally both). Someone can lack capacity at one point and have capacity later.
Capacity can fluctuate
Some conditions—especially dementia, delirium, and the effects of medication—can mean you have clearer periods. That’s why timing and careful attendance notes matter.
Capacity is decision-specific
Capacity isn’t a general “pass or fail” label. You might be perfectly able to make a simple Will but struggle with a very complex estate plan involving multiple trusts, business assets, or unusual provisions.
How modern solicitors assess testamentary capacity in practice
A solicitor’s job isn’t to “diagnose” you. It’s to make sure your Will is valid, your wishes are properly recorded, and the process can be defended later if anyone questions it.
Here’s what a careful capacity-focused Will process typically involves.
1) Seeing you alone (and checking for pressure)
If a beneficiary is present, hovering, “helping”, or answering questions for you, that’s a red flag. A good process involves seeing you privately—at least for the key parts—so your instructions are clearly your own.
If you’re worried about disputes in general, it can also help to understand the litigation landscape: Civil litigation.
2) Having a proper conversation (not a tick-box chat)
A real capacity assessment isn’t a form. It’s a conversation that tests understanding in a natural way. For example, you may be asked:
- What is a Will meant to do?
- Who are the people closest to you (partner, children, dependants)?
- What do you own in broad terms (property, savings, investments)?
- Who have you chosen as executors, and why?
- Why have you included or excluded certain people?
A good solicitor will ask you to explain things in your own words, and will record that.
3) Checking “orientation” without being patronising
You don’t need to get every date right. But if you’re confused about basic facts—where you are, who people are, what you’re signing—that’s a warning sign that needs further steps before proceeding.
4) Looking for triggers that make capacity harder to evidence
Certain situations are more likely to lead to a later challenge, even if you did have capacity. Examples include:
- a major change from a long-standing previous Will
- cutting out close family without explanation
- giving significant benefit to a new friend, neighbour, or carer
- instructions made during a hospital admission
- instructions made shortly after bereavement or major trauma
- “unusual” instructions that don’t fit with past behaviour or relationships
When those are present, a solicitor may recommend extra protection.
Banks v Goodfellow vs the Mental Capacity Act: why the Will test is different
You might hear professionals refer to the Mental Capacity Act 2005 (MCA). That law governs capacity in many day-to-day and financial contexts.
But testamentary capacity is assessed under the Will-specific test (Banks v Goodfellow). The MCA principles can still be relevant in practice—especially around supporting communication and helping someone make their own decision—but the legal test for Wills remains its own thing.
This is one reason people get caught out. A family might assume that because someone couldn’t manage finances or needed help with care decisions, they automatically couldn’t make a Will. That simply isn’t a safe assumption.
Medical evidence: when it’s needed and what it should cover
Sometimes the safest route is to obtain medical evidence—particularly where capacity is borderline, fluctuating, or likely to be challenged.
When medical input is commonly recommended
- a diagnosis of dementia or cognitive impairment
- recent delirium, infection, or hospital stay
- heavy medication affecting alertness or comprehension
- a significant departure from earlier Wills
- expected family conflict (for example, disinheriting close relatives)
What good medical evidence looks like
It’s not enough for a clinician to say “they seem fine”. A useful medical opinion should address the Banks v Goodfellow elements in plain terms and, ideally, confirm:
- the person understood they were making a Will and the effect of it
- they understood broadly what they owned
- they understood who might expect to benefit
- there was no mental condition affecting the decision-making behind the Will
Depending on the circumstances, that medical input might cost a few hundred pounds (£) or more—particularly if a specialist report is required. The cost can be frustrating, but it is often far cheaper than a disputed estate later.
Communication issues that can look like “lack of capacity” (but aren’t)
In real disputes, capacity challenges sometimes arise because the person wasn’t supported properly during the process.
For example:
- hearing loss (they didn’t fully hear the questions)
- English not being their 1st language (they agreed without truly understanding)
- speech difficulties after stroke (they couldn’t express themselves clearly)
- anxiety or distress (they shut down in a formal setting)
A good Will process adapts. That might mean slower meetings, shorter sessions, the right interpreter, written summaries, or meeting at the person’s best time of day.
Practical risk-reduction: what you can do to make your Will harder to challenge
If you’re in a higher-risk category, you don’t need to panic. You just need a process that stands up later.
Keep your instructions consistent and recorded
If you’re making big changes, explain why. That reason can be recorded in the file and, where appropriate, a separate letter explaining your thinking.
Choose the right executors
Executors don’t just “sign forms”. They manage the administration, paperwork, tax, and distribution. Where capacity might be questioned, the right choice matters even more—because your executors may need to defend the Will process later.
You may find this helpful if you’re planning in the context of dementia: Choosing executors and trustees when a testator has Alzheimer’s.
Consider whether you also need an LPA
A Will deals with what happens after death. A Lasting Power of Attorney helps while you’re alive, if you ever can’t manage decisions yourself.
If you want your attorneys to act together for extra safeguards, read: Joint Lasting Power Of Attorney Solicitors.
If you run a business and want continuity protection, see: Business Lasting Power Of Attorney Solicitors.
Avoid DIY documents if there’s any doubt
Homemade Wills are often challenged not because the person lacked capacity, but because the document is unclear, improperly executed, or created in circumstances that look suspicious.
If you’re in a risk category, professional drafting is not about being “fancy”. It’s about making sure the Will works and the evidence is there.
What happens if capacity is challenged after death?
If someone challenges the Will on capacity grounds, it usually becomes a dispute where the court looks at:
- solicitor attendance notes
- the circumstances of instruction and signing
- medical records and clinical evidence
- witness evidence from people who saw the person around that time
- the “logic” and context of the Will provisions
This is exactly why the process matters. The strongest protection is done before the Will is signed, not after someone dies.
A simple checklist: if you’re worried about capacity, do this
If you want a Will that is less vulnerable to challenge, here’s a practical starting point:
- Make the Will sooner rather than later (don’t leave it until a crisis)
- Have the solicitor see you alone for instructions
- Ensure the meeting is at your best time of day
- Bring clear details of key assets (home, savings, pensions, investments—high level is fine)
- Explain any major changes from previous Wills and why
- Consider medical confirmation if there’s any realistic risk of challenge
- Use appropriate witnesses and keep the signing process clean and documented
Speak to Atalaw Solicitors
If you’re making a Will where capacity could later be questioned, you don’t need a complicated process—you need a careful one. Atalaw Solicitors can guide you through clear instructions, practical safeguards, and robust drafting so your wishes are properly protected.
To discuss your situation, contact us here: Contact Us.
If you’d like to know more about the firm, you can also read: About Us.