Mental Capacity And Legal Authority: Bridging The Gap For Vulnerable Young People

For most families, a child's eighteenth birthday is a proud moment. It signals independence, the start of adult life and a chance to make choices about education, health and money. For parents of young people with learning difficulties, autism or long-term conditions that affect how decisions are made, the same moment can feel very different. The legal position changes overnight. Authority that once belonged to parents no longer applies, and conversations with their child's doctors, bank or school that used to happen easily, suddenly stop.

That shift can be deeply unsettling. The law presumes that every adult has the mental capacity to make their own decisions unless proven otherwise. It is a fair and important principle, designed to protect autonomy, but it often leaves families and young people navigating an unexpected and uncomfortable gap between care and control.

What mental capacity means in practice

The Mental Capacity Act 2005 provides the legal framework for how mental capacity is assessed and protected in vulnerable people. It primarily focuses on ability, not diagnosis, outlining that a person is thought to have capacity if they can understand, retain, weigh and communicate the information needed to make a specific decision.

The Act doesn't assume that capacity is an all-or-nothing concept, instead it respects that whilst a young person may be able to decide what to eat or which clothes to wear, they may still struggle to comprehend financial matters or medical treatment. It was created to support independence wherever possible, placing an expectation on professionals to presume capacity and to help individuals make their own decisions before concluding that they cannot.

For many families caring for a child with significant needs, the reality of this will feel far less empowering than it sounds, and this is because when a young person turns eighteen, the legal authority of parental responsibility ends.

Parents who have always acted in their child's best interests suddenly find they cannot access records, discuss medication or speak to social care teams without consent. Professionals, bound by confidentiality, may have no choice but to direct their discussions to the young adult, even where communication or understanding is limited. What the law sees as empowerment can, in practice, feel like exclusion.

The sudden loss of authority

The transition to adulthood happens in law on a single day, but emotionally it takes much longer. For parents it is often abrupt and confusing, and not simply because they wish to hold on to control but rather wish to maintain safety and consistency. They know their child's routines, fears and preferred communication style better than anyone else. Yet once that young person reaches adulthood, professionals may be unable to share information or accept parental input.

The result is what many families refer to as "the gap" – a space where legal independence exists on paper, but practical support has not yet caught up. It can leave vulnerable young people exposed to risk and parents unsure of what they are still allowed to do.

Bridging the gap

The good news is that there are ways to bridge this gap, provided planning happens early. The right approach for this will depend primarily on whether the young person has the capacity to make their own decisions.

If they do, they can create a Lasting Power of Attorney (LPA). One LPA covers health and welfare, the other property and financial affairs. These documents allow a young person to appoint trusted people (often parents or carers) to make decisions on their behalf if they later lose capacity. For many families, the process of creating an LPA is quite liberating. It allows the young person to express trust, while ensuring that those who know them best can step in when needed.

If, however, the young person lacks capacity, they will not be able to grant an LPA. In that case, families can apply to the Court of Protection for a deputyship order. A deputyship order authorises a parent or carer to make certain decisions, such as managing money, under the supervision of the court. Each order is tailored to the individual's needs, offering both flexibility and accountability.

The deputyship application process can take many months, so beginning the conversation before the young person's eighteenth birthday can help mitigate difficulties that might otherwise arise when decisions cannot be made.

Supporting decision-making

At the heart of the Mental Capacity Act is a message about respect. When it comes to mental capacity, individuals should not jump to conclusions. The Act encourages everyone involved (such as families, doctors, and social workers, etc) to support individuals in making their own choices wherever possible. That might mean presenting information in clearer terms, using visual aids, or giving extra time for discussion. Sometimes what looks like a lack of capacity is really just a lack of accessible communication.

Parents and carers often play a crucial role in making that support work. They understand how their child communicates, what helps them feel safe, and how they show understanding. Recognising that experience is vital. Legal frameworks work best when they value family insight rather than shut it out.

The emotional impact on families

For many families, the legal change at eighteen is not just procedural, it's personal. Parents who have spent years advocating for their child's welfare often feel invisible overnight. The professionals they had previously worked with begin speaking to the young person directly and, with the best of intentions, may exclude those who understand their needs most. It can feel like a loss of trust, even when everyone is trying to do the right thing.

The practical effects are just as real. Benefits can be delayed if a young person cannot complete paperwork. Treatment may be postponed while clinicians wait for formal consent. Bank accounts can be frozen, disrupting essential payments. These small hurdles can accumulate, creating stress for families who are already coping with the challenges of care.

How early advice can help

Taking legal advice before the age of eighteen can help families to prepare calmly and avoid disruption. A solicitor experienced in mental capacity and Court of Protection work can assess whether a young person is likely to have the capacity to make an LPA, guide families through the deputyship process where necessary, and liaise with professionals to make sure decisions are managed sensitively and lawfully.

Becoming an adult should not mean losing support. With thoughtful planning, it is possible to balance independence with protection, ensuring that young people with complex needs can move into adulthood safely and with dignity.

At Buckles, we understand that this area of law is not just about documents and forms. It is about protecting relationships and ensuring continuity of care. Every family wants the same reassurance – that their loved one will continue to be supported by people who understand them, and that decisions about their welfare will be made with both compassion and authority.