To make a valid Will, you must have 'testamentary capacity' — the mental ability to understand what you're doing and make informed decisions about your estate. This is a legal requirement that cannot be bypassed.
The test for testamentary capacity comes from the case of Banks v Goodfellow (1870) and requires that you: understand the nature and effect of making a Will, understand the extent of your property, understand the claims of those who might expect to benefit, and be free from any disorder of the mind that influences your decisions.
In 2026, as the UK population ages, mental capacity is an increasingly important consideration. Conditions such as dementia, Alzheimer's disease, and stroke can all affect capacity.
It's important to note that having a diagnosis of dementia does not automatically mean you lack capacity to make a Will. Capacity can fluctuate, and many people in the early stages of dementia retain sufficient capacity.
If there's any doubt about capacity, we may recommend obtaining a medical assessment before the Will is signed. This provides evidence that can be used to defend the Will if it's later challenged.
This is one of the strongest arguments for making a Will sooner rather than later. By the time capacity becomes an issue, it may be too late to create a valid document.
At Castle Family Legal, we're experienced in assessing capacity sensitively and can arrange medical assessments where needed. Don't leave it too late — contact us today.
