Guardianship vs Supported Decision Making: What Changes When Your Child Turns 18

For parents who have managed every aspect of their child's life — medical appointments, NDIS plans, school decisions — the approach of their child's 18th birthday raises an uncomfortable question: do we need to get formal legal authority to keep doing what we're doing?

The short answer is: almost certainly not, and attempting to do so may cause more problems than it solves.

Australian law presumes that when a person turns 18, they have legal capacity to make their own decisions. This presumption applies regardless of disability. The default is legal autonomy — not guardianship. For families accustomed to making decisions on behalf of a child with disability, this shift requires a genuine change in mindset, not just in paperwork.

What Legal Capacity Actually Means

Legal capacity — the ability to make decisions that are legally binding — is presumed for all adults in Australia. This means:

• An adult with an intellectual disability can enter contracts, sign documents, manage their own finances, and make health decisions
• A disability diagnosis does not, by itself, remove legal capacity
• The presumption of capacity can only be rebutted by evidence, in a formal process, for a specific decision or domain

In practice, this means that when your child turns 18, they are legally able to make their own decisions. Whether they want your involvement in those decisions, and in what form, is a matter of relationship — not legal authority.

For decisions where your child needs help — understanding a complex NDIS plan, navigating a medical appointment, managing finances — the appropriate response is supported decision making, not substituted decision making through a guardianship order.

What Is Supported Decision Making?

Supported decision making (SDM) is a framework that enables people with disability to make their own decisions with the assistance of trusted people who help them understand information, consider options, and communicate their choices.

Under SDM:

• The person with disability remains the legal decision-maker
• Supporters help them understand complex information
• Supporters do not override the person's preferences or substitute their own judgement
• The person's choice is respected even if supporters disagree

SDM can be documented in writing as a voluntary arrangement that names who the supporters are and what kinds of decisions they assist with. The legal effect and available formal arrangements depend on the state or territory.

For NDIS purposes, a supporter can assist with plan reviews, communicate with the NDIA on the person's behalf (as a correspondence nominee), and help implement plan goals. This is distinct from a formal plan nominee arrangement, which can make decisions about the participant's NDIS plan.

Formal Nominee Arrangements Under the NDIS

When a young person turns 18, any childhood nominee arrangement should be reviewed and an adult arrangement established if ongoing family involvement is needed. There are two distinct NDIS nominee roles:

Plan nominee: Makes decisions about the preparation, management, and use of the participant's NDIS plan on the participant's behalf.

Correspondence nominee: Manages communications with the NDIA — receiving plan documents, attending planning meetings, and communicating plan decisions on the participant's behalf.

These are separate arrangements and can be held by different people. They do not confer legal guardianship or the ability to override the participant's own choices.

Setting up post-18 nominee arrangements is a practical step for families of participants who need ongoing family involvement in NDIS management. It must be actively arranged with the NDIA — childhood arrangements do not automatically transfer.

When Is Guardianship Appropriate?

Formal guardianship — an order from a state or territory guardianship tribunal (such as VCAT in Victoria, NCAT in NSW, or QCAT in Queensland) — gives a guardian legal authority to make decisions on behalf of another person. It is a significant legal intervention and should be treated as a genuine last resort.

Guardianship is appropriate only where:

1. The person genuinely lacks the capacity to make a specific type of decision, even with supported decision making
2. There is a real and ongoing need for someone to have legal authority to make that decision
3. The guardianship order is limited in scope to the decisions where capacity is absent
4. The decision cannot be adequately addressed through less restrictive means

Guardianship decision-makers generally consider whether less restrictive alternatives are sufficient, but the test and process vary by jurisdiction. If supported decision making with appropriate assistive supports can address the need, formal guardianship may not be necessary.

For most families of young adults with intellectual disability, the practical decisions that need managing — attending medical appointments, coordinating NDIS services, managing daily finances — can be handled through supported decision making, informal family support, and nominee arrangements. Guardianship adds legal complexity and may add costs and formal review or reporting requirements without practical benefit for families who already have the person's trust and involvement.

Financial administration (analogous to guardianship but for finances) is a separate but related consideration. If a young adult is at significant risk of financial exploitation or cannot manage money safely even with support, a financial administration order may be warranted. But again, this is a last resort — not a default response to the 18th birthday.

The Practical Steps Before the 18th Birthday

The transition of legal status at 18 requires several practical steps, regardless of whether guardianship is pursued:

1. Set up NDIS nominee arrangements. Contact the NDIA before the birthday to understand the process for establishing adult plan and correspondence nominees. Arranging them in advance can support continuity where family involvement is wanted.

2. Update Medicare and myGov. Confirm the young person's Medicare enrolment and card arrangements, and set up their own myGov access. If they need assistance managing these, ask the relevant agency about authorised access arrangements.

3. Establish a bank account in the young person's name. If they don't already have one, an adult bank account should be established, with appropriate account access or online banking support if needed.

4. Discuss healthcare consent. Adult medical decisions belong to the adult patient. Discuss with treating doctors how family involvement in medical appointments will be structured going forward — ideally with the young person's explicit consent.

5. Document supported decision making. If your child wants your ongoing involvement in specific types of decisions, record the person's choices about who supports them and in what way, using an arrangement available in your state or territory where appropriate.

6. Talk to an advocacy organisation. If the family has genuine concerns about the young person's capacity to make safe decisions in specific domains — finances, health, accommodation — consult a disability advocacy organisation or public advocate before pursuing formal guardianship. They can provide an honest assessment of whether SDM is sufficient.

The transition to adult legal status is not something to manage alone. The Australia Post-Secondary Transition Roadmap includes a step-by-step guide to the legal and administrative changes at 18, covering NDIS nominees, Medicare, Medicare cards, bank accounts, and the difference between supported decision making and formal guardianship — with the specific timing for each action built into the transition timeline.

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