No. At 18 your parental responsibility ends and your child is legally presumed to make their own decisions. Where they cannot make a decision, it is made in their best interests under the Mental Capacity Act 2005.
What actually changes at 18
Parental responsibility, the legal right and duty to make decisions for your child, ends on their 18th birthday. From that point the law treats your son or daughter as an adult who decides for themselves about their health, their money, where they live and who can be told about them. That is why a hospital, college, social worker or bank can suddenly say you no longer have the right to decide or to be given information. It does not mean you have lost all standing, but it does mean your standing now flows from your child's own decisions, or from a formal legal appointment, rather than from being their parent.
The framework that governs all of this is the Mental Capacity Act 2005. Its starting point is that every adult is assumed to have capacity unless it is shown otherwise, that they should be given all practicable help to decide before anyone concludes they cannot, and that an unwise decision is still their decision to make.
The two things most parents are not told
First, the Mental Capacity Act applies in England and Wales from age 16, not 18. So the shift in your role begins two years earlier than the 18th birthday many parents brace for, and capacity is judged decision by decision. Your child may be able to choose what they eat or wear but not manage a bank account, so "my child lacks capacity" is never a blanket status; it always attaches to a specific decision at a specific time.
Second, if your child cannot make a particular decision, a Lasting Power of Attorney is not a route open to you. An LPA can only be created by the young person themselves while they still have the capacity to make it. For a young adult who lacks that capacity, the parent instead applies to the Court of Protection to be appointed a deputy: for property and financial affairs, or for personal welfare, or both. Welfare deputyships are granted only in the most difficult or disputed cases. In Scotland the equivalent is guardianship, and in Northern Ireland a controller.
Why this matters for what you do next
Where your child has capacity, the most useful thing you can do is help them put their own arrangements in place: a Lasting Power of Attorney, or simply their written consent for you to speak to their GP, college or bank. Where they genuinely lack capacity for the decisions that matter, any decision made for them must be in their best interests, taking account of their past and present wishes and consulting those who care for them, including you. You do not need a court order to be consulted; you do need one to hold legal decision-making authority.
For a clearer picture of how capacity is tested, see what a mental capacity assessment at 16 involves, and for the formal route to authority, what deputyship for a young adult who lacks capacity means.
Where the law comes from
Related
This page is general information, not clinical or legal advice.