Mental Capacity and Lasting Power of Attorney

18th August 2025

Updated:

24th September 2025

When it comes to making decisions about health, finances, or legal matters, mental capacity plays a critical role. Whether you’re helping a loved one apply for a Lasting Power of Attorney (LPA) or facing a situation where capacity is in question, one thing quickly becomes clear: determining capacity isn’t always straightforward.

What Is Mental Capacity?

Mental capacity is the ability to make and communicate decisions. Under the Mental Capacity Act 2005, every adult is assumed to have capacity unless proven otherwise. A person is considered to lack capacity if they cannot:

• Understand relevant information
• Retain that information long enough to make a decision
• Weigh up the options
• Communicate their decision in any way

It sounds simple in theory, but in practice it can be much more complicated.

The Grey Areas in Capacity Assessments

Mental capacity is not fixed. It can fluctuate day to day or even hour to hour, especially for people with conditions like dementia, stroke or mental illness. Someone may be capable of choosing what to eat for lunch, but unable to manage their bank account.

This is because capacity is both decision-specific and time-specific. That nuance often leads to hesitation, disagreement, and sometimes legal disputes.

Why Mental Capacity Matters for Lasting Power of Attorney

One of the biggest challenges comes when it’s time to create a Lasting Power of Attorney. LPAs must be made while the person still has full mental capacity. If that window of time is missed, or if there’s disagreement about whether capacity existed, the LPA could be rejected.

Worse still, families may have to go through the more expensive and time-consuming process of applying to the Court of Protection. This often happens when people leave it too late, hoping to “get around to it” eventually.

The Challenge of Professional Capacity Assessments

While a formal capacity assessment by a GP or specialist can help, they’re not always readily available, especially during times of crisis. And because capacity can fluctuate, even a professional’s assessment might only apply in that moment.

This unpredictability is one reason Power of Attorney Online encourages early action. Waiting until capacity is questioned is often too late.

The Takeaway: Plan Ahead While Capacity Is Clear

Capacity is a complex and sensitive issue. Not just medically or legally, but emotionally, too. Families often face tough conversations and difficult decisions. But starting early, while capacity is clear and confirmed, helps avoid complications and ensures your loved one’s wishes are honoured.

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