What Is Testamentary Capacity?

The legal test

To make a valid will in England and Wales, you must have testamentary capacity at the time you sign it. The legal test comes from a court case called Banks v Goodfellow (1870) and has remained largely unchanged for over 150 years.

You must:

1. Understand what a will is and what it does
2. Know the extent of your estate — not necessarily the exact value, but a general understanding of what you own
3. Understand the claims of those who might expect to benefit from your estate (family members and dependants, even if you choose to exclude them)
4. Not be suffering from any disorder of the mind that poisons your affections, perverts your sense of right, or prevents your judgment from being exercised freely

The fourth point is the subtle one. A person can have dementia or other cognitive impairment and still have testamentary capacity for a will, provided the impairment does not affect their understanding of those four elements at the moment of signing.

When capacity is questioned

Challenges to testamentary capacity typically arise after someone has died, when a family member believes the deceased lacked capacity when the will was signed — often because of dementia, stroke, serious illness, or strong medication.

To succeed in a challenge, the person contesting the will must usually show that the deceased lacked capacity at the time of signing, not just at some point before or after. Temporary lucidity is sufficient. A person in the middle stages of dementia may have periods of clear understanding — and a will made during one of those periods can be valid.

How to protect a will from challenge

If there is any possibility that your capacity could be questioned — because of age, illness, or family circumstances — there are practical steps worth taking when you make your will.

Have your GP or a doctor assess your capacity before you sign, and ask them to write a brief note confirming their assessment. This does not need to be elaborate; it just needs to exist.

Have the will witnessed by people who know you and can attest that you appeared to understand what you were doing.

Write a letter of wishes explaining your decisions in your own words. An explanatory letter that clearly articulates your reasoning is strong evidence of capacity.

Capacity and PureWill

PureWill's online process is designed for people who have full capacity and are making a straightforward will. If you have any doubts about your own capacity, or if a family member is asking you to help them make a will and their capacity might be questioned, please seek advice from a solicitor. This is one of the situations where professional involvement is genuinely worth having.