Can someone with dementia still make a valid will?

Yes, often. A dementia diagnosis does not stop someone making a valid will. The law does not ask what condition a person has. It asks whether, at the moment the will is made, they understood what they were doing, judged against a specific legal test. A solicitor's job is to apply that test properly and record how it was met, so the will stands if questioned later.

The test the courts use

The test is called testamentary capacity. It was set out by a court in 1870 in a case called Banks v Goodfellow, and it is still the test today. The courts confirmed this as recently as 2021. The Mental Capacity Act 2005 governs most decisions about a person's health and money, but for wills the older test applies.

To have capacity to make a will, the person must:

• Understand what a will does. That it says who gets their property when they die, and that it replaces any earlier will.
• Have a rough idea of what they own. Not a balance sheet, but a fair sense of the house, the savings and anything else of real value.
• Understand who might expect to benefit. A spouse, children, anyone who depends on them. They need not leave those people anything, but they must be able to weigh them.
• Not be suffering from a disorder of the mind that poisons the decision. A false belief about a child, say, that leads to that child being cut out.

What dementia does and does not do to capacity

Dementia progresses at different speeds in different people. For the law on wills, four things matter.

• Capacity is decision-specific. Someone can lack the capacity to manage their finances and still be able to make a will, because the will test is different. How much understanding it needs depends on how complex the will and the estate are.
• Capacity is judged at the moment of signing. A diagnosis last year says nothing certain about the afternoon the will is made.
• It fluctuates. Many people with dementia have better and worse days, and better and worse times of day. A will made in a lucid period, what solicitors call a lucid interval, is valid, and the law has recognised this for well over a century.
• The early stages are often fine. Many people with mild dementia still meet the test. The difficulty comes later, at a point that differs for everyone.

Where a will is properly signed and looks rational, the law also presumes capacity. A challenger has to raise a real doubt first. A diagnosis does not prove a lack of capacity, but it can raise that doubt. Those relying on the will must then prove capacity. That is why careful evidence matters more, which is where the golden rule comes in.

How a solicitor tests and records capacity

The golden rule is guidance the courts gave solicitors decades ago. Where a client is elderly or seriously ill, the solicitor taking the will should ask a doctor to assess capacity and record the assessment or witness the will. It is not a legal requirement, and a will made without it is not invalid for that reason. It makes sure the evidence exists before anyone needs it. With a client who has dementia, it looks like this.

• A letter from the GP or the memory clinic. Aaron writes to the doctor setting out the Banks v Goodfellow test in plain terms. He asks whether the client meets it. A note saying the patient seems well is not enough. Where there is real doubt, an old age psychiatrist or specialist capacity assessor produces a full report.
• A meeting with the client alone. Family wait outside, however well meaning. The client explains in their own words what they own and who is in the family. They say what they want and why.
• Plain questions, not a quiz. What is a will for. What do you own, roughly. Who might expect something. Why this way. If the answers show understanding, the test is met.
• A detailed attendance note. Aaron writes down what was asked and answered, in the client's own words where possible. He also records who was present, and his own view on capacity and why. The note is kept with the will.

Why it matters later: a challenge on capacity usually comes years after signing. By then the person who made the will has died and cannot explain themselves. The doctor's letter and the attendance note are then the evidence. A will with both is hard to overturn. A will with neither invites the argument.

What makes a will challengeable

Capacity is one ground. There are others, and they come up more often where the person was ill or depended on someone.

• Undue influence. Pressure that overbears the person's own wishes. Persuasion is not enough, it has to amount to coercion, and the challenger has to prove it. But suspicion arises easily where a carer or one child is the main beneficiary.
• Lack of knowledge and approval. The person must know what is in the will and approve it. Where someone who benefits arranged it, or the person could not read it, or it departs sharply from what they had always said, a court will want proof the contents were explained and understood.
• A family member arranging it. If a son gives the instructions, sits in on the meeting and pays the bill, and the will favours him, it starts on the back foot. The instructions must come from the person making the will.
• A homemade will. A will form filled in at the kitchen table, with no independent view on capacity and no record, is the easiest kind to attack. It may be perfectly valid. There is just nothing to prove it.
• No record. A will can lose a challenge not because the person lacked capacity, but because nobody can now prove they had it.

If a later will fails, the previous valid will takes its place. If there was none, the intestacy rules apply.

If capacity has already gone

Once a person no longer meets the test, a will they sign will not be valid. Two things people often assume are not true.

• An attorney under a lasting power of attorney cannot make or change the person's will. The LPA covers money and property. Making a will is outside it.
• Nor can a deputy appointed by the Court of Protection. The Mental Capacity Act 2005 says so.

The only route is a statutory will, made by the Court of Protection on an application by someone with an interest, usually a family member, attorney or deputy. The court decides what is in the person's best interests, giving weight to their past and present wishes, feelings, beliefs and values. It then authorises a will on those terms. The application fee is £432, with a further £266 if the court holds a hearing, and the fees are set out on GOV.UK. Add medical evidence and legal work, and expect months. It works, but it is slower, dearer and less certain than the person making their own will while they could.

A short example. Joan is 81 and was diagnosed with Alzheimer's disease in the spring. Her will from 1999 leaves everything to her three children equally. She wants to add £5,000 to each of her four grandchildren. Seen now, with a GP letter and a meeting alone, that is a straightforward new will. Left two years, until she no longer meets the test, it means a statutory will application, £432 in court fees before anyone is paid for the work, medical reports and a wait of many months, for a change she could have made in an afternoon.

Practical steps to take now

• Act early. Every month of delay narrows the window. A will made now with good evidence behind it is far more likely to stand. The same will in three years may not be possible.
• Bring the diagnosis into the open. Tell the solicitor at the first call. It is not an obstacle, it is the reason to do the job properly, and a solicitor who does not know cannot follow the golden rule.
• Make lasting powers of attorney at the same time. Capacity to make an LPA is a separate test, but the same window is closing. LPAs made now usually avoid a deputyship application later. The OPG fee is £92 per document, and registration usually takes 8 to 10 weeks, sometimes longer. The guide to dementia and power of attorney covers this. The guide to losing capacity without an LPA shows what happens if it is left too late.
• Keep the existing will safe. If a new will proves impossible, the old one applies. Find the signed original and make sure the executors know where it is.

What to do next

Check the facts first: where the existing will is, what it says, and what the person wants to change. Then talk to a regulated solicitor, and say at the outset that there is a diagnosis. Aaron offers a free 15-minute call. He visits clients at home across East and North Yorkshire. For someone with dementia, home is often where they are most settled. He meets the client alone and asks for the medical evidence the golden rule calls for. He keeps the record that helps the will stand if it is challenged. Wills and lasting powers of attorney are each a fixed fee, agreed in writing before any work starts. The Plan Finder gives a steer before you call. Aaron is a solicitor regulated by the SRA and a full member of STEP.

This page is general information about the law of England and Wales. Whether a particular person can make a valid will depends on their own facts on the day.