The day your child turns eighteen, the law changes overnight.
You wake up the same parent. Your child wakes up in the same bedroom. Nothing looks different. But legally, everything is.
In Missouri, eighteen is a hard line. At midnight, your son or daughter becomes an adult in the eyes of the state. The law now presumes they are competent. It does not matter if they have Down syndrome. It does not matter if they are on the autism spectrum. It does not matter if they cannot balance a checkbook or explain their medication. The presumption is automatic.
And with that presumption, your legal authority as a parent ends.
You are no longer a “natural guardian.” You are a third party. That means a hospital cannot automatically share medical information with you. A bank cannot discuss an account. A college cannot speak with you about grades or discipline. Social Security will not talk to you without paperwork. Even confirming that your child is in an emergency room can become a legal problem.
Most families discover this in a crisis. A late-night phone call. An ER visit. A form pushed across a counter. There is a way to prepare for that moment. But it requires planning before the birthday.
Start With the Presumption of Competence
Every adult in Missouri is presumed capable of managing their own affairs unless a court says otherwise. That standard is high. It requires clear and convincing evidence. So the default position of the law is independence.
For some young adults with disabilities, that presumption works just fine. They may need help reading contracts or navigating insurance, but they can express choices. They can say, “I want Mom to help me.” In those cases, the cleanest solution is a Durable Power of Attorney.
What a Durable Power of Attorney Actually Does
A Durable Power of Attorney—often called a DPOA—is a private document. It is not a court case. It is not public. It is a voluntary delegation of authority. Your adult child signs it. They choose who helps them.
A Power of Attorney is based on permission. Your child remains the decision-maker. They are the principal. They are not stripped of rights. They are not declared incapacitated. They are appointing someone they trust to step in when needed.
In Missouri, the document must be written and signed before a notary. And it must contain specific language stating that the authority continues even if the person becomes disabled or incapacitated. That durability language is not optional. Without it, the document fails at the exact moment it is most needed.
The practical question is this: does your child understand, at a basic level, what they are signing? They do not need to understand tax law or investment strategy. They do need to understand who they are appointing and that this person will help with medical or financial decisions. If they can express that preference—even in simple terms—a Power of Attorney is usually appropriate. If they cannot understand that concept at all, you may need to consider guardianship.
What a Financial Power of Attorney Covers
A well-drafted financial Power of Attorney in Missouri can authorize an agent to open bank accounts, write checks, manage investments, apply for Medicaid, deal with Social Security, file tax returns, and handle real estate. It can also nominate a preferred guardian if a court case is ever filed later. That nomination carries real weight.
But there are limits. An agent cannot rewrite a will. They cannot force the principal to act against their will while the principal is still capable of communicating. A Power of Attorney allows help. It does not allow control.
Healthcare Requires a Second Document
Missouri separates financial authority from medical authority. A Healthcare Power of Attorney allows your adult child to name someone to make medical decisions if they cannot. That authority usually begins when a physician certifies incapacity. By default, Missouri requires certification from two physicians.
In an emergency room at two in the morning, that delay can matter. Missouri law allows you to opt into a one-physician certification instead. That is a small checkbox with enormous practical consequences. For families dealing with seizure disorders, mental health crises, or unpredictable medical complications, that choice should be deliberate.
There is also the Health Care Directive—sometimes called a living will. This covers end-of-life decisions. Missouri is particularly strict about artificial nutrition and hydration. If your child would want tube feeding withheld in certain conditions, that authority must be explicitly granted in writing. Without specific language, an agent cannot authorize it.
Permission to Know Is Different From Power to Decide
A Healthcare Power of Attorney gives you the right to decide. It does not automatically give you the right to know.
Federal privacy law—HIPAA—creates a wall around medical information. Without a signed HIPAA authorization, hospital staff may refuse to share lab results, treatment notes, or even confirm that your child is admitted. I have watched parents stand at a nurses’ station and be told, politely, that the staff cannot discuss anything.
A standalone HIPAA authorization solves that. It can be broad or narrow. It can include mental health records and substance abuse treatment, or exclude them. It can last indefinitely. It does not require a notary, though many families include it with the rest of their documents.
For high-functioning young adults heading to college, this is often the most important document. They may want to make their own decisions. They may not want a parent directing treatment. But they do want someone who can see the paperwork and help interpret it. Permission to know is different from power to decide.
When Guardianship Becomes Necessary
Guardianship is not a form. It is a lawsuit.
If your child cannot understand what a Power of Attorney is, cannot communicate a preference, or is at serious risk of harm or exploitation that voluntary documents cannot address, Missouri probate court may be necessary. Under Chapter 475, a court can declare someone incapacitated and appoint a guardian for personal decisions and a conservator for financial management.
This is public. It requires medical evidence. The court appoints an attorney to represent your child’s interests. The standard of proof is clear and convincing evidence. Why would a family choose this route? Because a Power of Attorney is permissive. It cannot force compliance. If an adult with significant cognitive impairment refuses necessary placement, refuses medication, or is being manipulated financially, an agent under a POA has limited enforcement power. A guardian, appointed by a court, can make decisions even over objection. For a full explanation of that process, see our guide on Missouri guardianship.
What Families Should Actually Do
First, start the conversation before eighteen. Seventeen and a half is not too early. Ask direct questions. Can your child explain who they trust to help them? Can they articulate, even simply, that they want assistance with medical or financial matters?
Second, if capacity exists, draft comprehensive documents: a Durable Financial Power of Attorney, a Healthcare Power of Attorney with deliberate choice about one-physician certification, a Health Care Directive with specific authority where needed, and a HIPAA authorization. Name successor agents. Life happens. Parents age.
Third, if capacity does not exist, prepare to file for guardianship immediately upon the eighteenth birthday. Do not wait for a crisis. Courts move deliberately. Paperwork takes time. Medical affidavits must be gathered.
And while you are building legal authority, do not overlook the financial side. A Special Needs Trust protects benefits eligibility for larger assets, and a MO ABLE account gives your young adult day-to-day financial flexibility without jeopardizing SSI. The legal and financial pieces belong together.
The goal is not control. It is protection with dignity. Missouri’s framework is built around supported autonomy. The law begins with independence and only moves toward restriction when necessary. That is not an obstacle. It is a safeguard.
The cliff at eighteen feels abrupt because it is. One day you sign school permission slips. The next day you are told you cannot see medical records without paperwork. But this transition does not have to be chaotic. With the right documents in place, parents remain involved. Adult children retain their status and dignity. Medical crises become manageable. Financial management becomes structured.
Eighteen is a legal boundary. It does not have to be a wall. Plan before you reach it.
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The Legal Cliff at Eighteen
