Understanding Mental Capacity: Why It's Not As Simple As You Think

By Neha Mehta | Chartered Accountant, Financial Coach and SEND Parent

It's been a while since my last article. Life got busy with juggling school holidays and work, and I have learned with time to be kind to myself. But I haven't got my foot off the accelerator completely. I have been researching, reading and having lots of conversations to understand mental capacity, what it means, and how it's assessed. The more I researched it, the more I realised just how subjective it is, and how much more there was to say than I first thought.

If you're a parent of a child with brain damage, you'll know this question well. Will my child have mental capacity when they become an adult? When I first started learning about mental capacity, I assumed people either had it or they didn't. The truth is far more nuanced, and in many ways, far more reassuring.

Capacity is not binary

Mental capacity is a person's ability to make a particular decision at a particular time. Capacity is not a blanket Yes or No for everything across their life. A person can have capacity to decide what they want for lunch and still need support to pay for that lunch.

I keep see-sawing on this when it comes to my daughter, and that is exactly because of how subjective it is. I can see that she has some capacity. What that will look like when she becomes an adult is a question that I can only have an answer to when I arrive at that bridge. What I do know is that I want to understand her capacity and support her to make as many of her own decisions as possible. She needs to know where she has choices, and how to weigh up those choices to the best of her ability.

Thinking in buckets

This has led me to think about mental capacity in different buckets, depending on the scenarios, ability and decision impact. Let me share a couple of examples to show how I think about it.

Take clothes. Does she have the capacity to decide what she wants to wear? Absolutely, yes. If what she chooses is not right for the weather, that is something she needs to learn for herself. So I let her wear it, and I quietly pack a change of clothes for when she realises and wants to change. That is a low stakes decision, and a mistake that is easy to fix.

Money is another bucket entirely. She is still young, and numbers are not her strong point. But she still needs to learn to make choices. I always give her options and explain, in the best way I can, what each one means. Then within the set boundaries, the choice is hers. If the money is gone, it is gone. It might be as simple as choosing between buying an ice cream or a chocolate. Her understanding is still limited, and the point is not to test her. The point is to see how much more she can develop through everyday decisions like these.

Four more scenarios worth thinking through

As she has got older, the scenarios have got harder. Here are four I find myself working through right now.

Friendships and relationships. There are a limited number of people I trust her with, but the ones I do trust, I trust because I know they will act in her interest. When she goes out with one of them, I step back. I let them decide. If she needs new clothes, I lean on a much younger friend of mine to take her shopping, because left to my own choices, she would end up dressed like a woman in her forties, which is exactly what I would pick. I keep reinforcing with her who she can trust, and at the same time I acknowledge who she is comfortable with, and for what. It is subjective, every single time.

Safety and risk. This one is trickier, because she is at the age where she wants independence. For her that means going for a walk alone, being left at home while I nip to the shops, or cutting her own nails. We have had many conversations, and a few arguments, about the walk. I ask her what she would do if a stranger approached her, how she would know who is a stranger, what she would do if someone got too close or touched her. She doesn't have answers yet. So I tell her, until you can answer those, we walk together. What I can do is give her some space within that. In the park, she runs or cycles ahead, and as long as I can see her, that's fine. Being left at home alone is a straight no for now, that's a boundary and she needs to respect it, not something we negotiate. Cutting her own nails was the opposite. That was her boundary to push, and mine to respect. It was nail-bitingly tense the first few times, watching her like a hawk, but I realised she needed to learn it. Now I let her get on with it and tidy up once she's done.

Health and body. This works differently again. A haircut is a negotiation. She hasn't properly learned to look after it herself yet, so whenever I think she could do with a trim, we talk about it. Sometimes she agrees, and I take the opportunity there and then. Sometimes it's a hard no, and I have to respect that. Medicine is the opposite, it is non negotiable. I tell her she has to take it until the doctor says she doesn't need it anymore, and that's that. It doesn't mean there's no drama around taking it, there often is, but there is no choice in it, not for her and not for me. Doctor and dentist visits sit somewhere in between. I explain what's happening, and as she's getting older, the doctor has started speaking to her directly too. Even though she still turns to me for answers, I give her choices where I can and let her decide, within the limits of what's actually in her best interest.

School and activity choices. These are simpler. For me, these should be fun, and they are entirely her call. As long as she is enjoying something and wants to keep doing it, we do it. The moment she doesn't, we stop. This one sits completely in her control, no negotiation needed.

Across all of these, my aim is always the same, to empower her as much as I possibly can. Sometimes that means stepping back completely. Sometimes it means holding a firm boundary. The two can look contradictory from the outside, but they come from the same place.

What this actually feels like

If I'm honest, the hardest part isn't any single decision, it's the constant tension between wanting to protect her and wanting to let her fail safely. What exhausts me more than any of the individual choices is that none of it gets easier with repetition. Every decision, every activity, every outing needs its own conversation, and my explanations to her are rarely simple. There's a lot of emotional work behind getting her to a place where she can even weigh something up, let alone actually choose. I don't get to set a rule once and be done with it. I reassess, over and over, because she is growing and changing, and so is what she's capable of.

And then there are moments like the activities, where none of that applies. She wants to do something, we do it. She doesn't, we stop. No negotiation, no risk assessment, no explaining consequences. Just her, choosing. Those moments are a relief. They're also, honestly, a source of real pride, watching her hold something that is completely and simply hers.

What the law says

So where does the law sit in all of this? In England and Wales, the Mental Capacity Act 2005 starts from a positive place. Everyone is assumed to have capacity unless it is shown otherwise, and a diagnosis alone does not take that away. Brain damage, a learning disability, autism, dementia or a mental health condition does not automatically mean someone lacks capacity. It is looked at for the specific decision.

An assessment looks at four things. Can the person understand the information they need? Can they hold onto it long enough to use it? Can they weigh it up, including the consequences? And can they communicate their decision in any form, such as speech, writing, gestures, signing or a communication aid? If someone cannot do one of these because of an impairment of the mind or brain, they may lack capacity for that decision. It is decision by decision, never a judgement on the whole person. And an unwise choice does not mean a lack of capacity.

How an assessment happens

It is not an exam with a pass mark, and there is no single certificate that says someone has capacity or doesn't. Each assessment is tied to one decision at one point in time.

Who does it depends on the decision. For everyday choices, the people supporting someone, like a parent, carer or teacher, can think it through by talking with them. For bigger decisions, it is usually the professional involved, such as a doctor for medical treatment, or a certificate provider for a Lasting Power of Attorney.

In practice, it is a conversation. The assessor explains the decision in language that suits the person, then explores whether they can understand it, hold onto it, weigh it up and communicate a choice in whatever way works for them. Before anyone decides a person cannot make a decision, the law says every practical step must be tried to help them, like simpler words, pictures, more time or a familiar person in the room.

What struck me most is how much judgement sits inside a formal legal process. In a borderline case, two reasonable assessors could land in slightly different places. That is not a flaw. It reflects how individual each person and each decision is.

Capacity can change

Capacity is not a one off test that settles things forever. It can be looked at again whenever a decision needs making, because capacity can change. What someone can do and understand shifts as they grow and learn, and our brains keep rewiring themselves throughout life. Neuroplasticity really is remarkable. For families, that is reassuring. We are not locked into one assessment made at one moment.

Where I still don't have the answers

I do not for a second believe my daughter will understand investments, so I already know she will need support with her finances long term, likely through a deputyship. But could she make a will one day? Or a Lasting Power of Attorney? Honestly, I don't know yet. Each is its own decision with its own test, and I will cross that bridge when I come to it.

Mental capacity is not a label you get given once. It shifts with the decision, the stakes, the person and the point in their life. If you have questions about wills, LPAs or deputyship for your own family, a solicitor who specialises in Court of Protection work is the right kind of professional to speak to.

For now, I will keep researching and sharing what I learn, and hopefully it helps you think through your own approach with your own child.

If you want to go deeper on LPAs, I have written about what they are and why they matter in Lasting Power of Attorney UK: What You Need to Know, and a practical walkthrough in How to Prepare for Your LPA.

If you are thinking about the wider plan for your child, I cover the Will and trust questions I asked first in What Happens to My Disabled Child When I Die?.

If you want to talk through how capacity, deputyship and trusts fit into the plan for your child, I offer a free 30-minute discovery call. Book a free 30-minute discovery call.

For educational purposes only. Not regulated financial or legal advice. For your own unique circumstances, please consult a solicitor specialising in Court of Protection work, disability and estate planning.