Understanding Mental Capacity to Make a Will: The Current Test and Proposed Reforms

When creating a Will, one of the most important legal requirements is that the person making it – known as the testator – has the mental capacity to do so. Without this, the Will may be declared invalid, potentially leading to lengthy legal disputes and distress for loved ones.

A lack of mental capacity is one of the most common grounds on which Wills are challenged in England and Wales. While the current test is based on a legal case from the 19th century, new proposals from the Law Commission aim to modernise this aspect of Will-making law.

Quick Summary: What Is Mental Capacity to Make a Will?

Currently, to make a valid Will, the person must:

• Understand what a Will is and its legal effect.
• Know roughly what assets they own.
• Consider who might reasonably expect to benefit.
• Not suffer from a mental disorder that affects their decision-making.

The Current Legal Standard: The Banks v Goodfellow Test

The legal test for mental capacity when making a Will was established in the historic case of Banks v Goodfellow (1870). The court ruled that, for a Will to be valid, the testator must meet four essential criteria:

• Understand the nature and effect of making a Will.
• Understand the extent of their property.
• Consider the claims of those who might reasonably expect to benefit.
• Be free from any mental disorder that influences decisions.

This test continues to govern testamentary capacity in England and Wales, though many legal professionals have highlighted the need to bring it in line with modern medical understanding.

Proposed Changes from the Law Commission

On 16 May 2025, the Law Commission published a major report into the modernisation of Wills law and testamentary freedom. Among its key recommendations is the proposal to replace the Banks v Goodfellow test with the capacity framework from the Mental Capacity Act 2005 (MCA).

This would bring the law in line with the broader approach used across healthcare and financial decisions, ensuring greater consistency in assessing whether someone has the capacity to make a Will.

Under the MCA 2005, a person is assumed to have capacity unless it is proven otherwise. Capacity is assessed based on whether the person can:

• Understand the relevant information.
• Retain that information long enough to make a decision.
• Weigh the information as part of the process.
• Communicate their decision.

This approach also recognises that capacity can fluctuate and be decision-specific, which is particularly important for people with dementia or those taking medication that may impair their judgement.

A New Code of Practice

The Law Commission also recommends a statutory Code of Practice to accompany this change. It would provide practical guidance for solicitors and medical professionals when assessing testamentary capacity under the MCA.

How Mental Capacity Is Assessed in Practice

Today, solicitors use the Banks v Goodfellow criteria when drafting a Will. This typically involves asking open-ended questions, discussing the person’s understanding of their assets and family, and recording observations in detailed notes.

In cases involving complex medical histories, cognitive impairment, or other concerns, a medical capacity assessment is often advised. A written opinion from a GP or mental health specialist can be vital if the Will is later contested.

If the proposed changes are implemented, professionals will likely follow the MCA’s assessment structure instead, supported by the new Code of Practice.

What Happens If Capacity Is in Doubt

If there is any uncertainty about capacity, these steps can help protect the Will:

• Keep detailed notes at the time of the conversation.
• Involve independent witnesses where possible.
• Request a formal capacity assessment from a medical professional.
• Use clear, simple language throughout the process.

If these steps are not taken and a dispute arises after death, the court will examine all available evidence to decide if the person had capacity when the Will was made.

How ELM Legal Services Can Support You

At ELM Legal Services, we take great care to ensure that every Will is legally sound and properly reflects our client’s wishes. Our experienced advisers assess capacity sensitively and thoroughly, and liaise with medical professionals when appropriate.

We also stay fully up to date with legal reforms and best practices, so our clients can feel confident that their Wills will stand up to scrutiny, now and in the future.

Frequently Asked Questions

Can a person with dementia make a Will?

Yes – dementia does not automatically mean someone lacks capacity. Each situation must be assessed based on the individual’s ability to understand and make decisions at the time.

What legal test is currently used to assess capacity to make a Will?

At present, the Banks v Goodfellow test is used. This may change if the Law Commission’s proposals to adopt the Mental Capacity Act framework are implemented.

What should I do if I’m worried about someone’s ability to make a Will?

Seek legal advice. It may be appropriate to involve a doctor to conduct a capacity assessment and to document the process carefully.

Will these legal changes affect my existing Will?

No. Any reforms will apply going forward. However, if there are concerns about capacity at the time your Will was made, a review could be helpful.

Conclusion

Ensuring that a Will is made with full mental capacity is essential to its legal validity and to honouring your wishes. If you or a loved one are concerned about mental capacity then getting professional advice is crucial.

Book a no obligation chat with one of our expert Wills experts by filling out our contact form, or calling us on 0117 952 0698 today.