At 18, parental authority ends, but guardianship is not automatic

What Ontario Law Says

These points come from the statute text and the Government of Ontario pages listed below. They are general information, not legal advice.

Adults are presumed capable

The Health Care Consent Act, 1996 presumes a person is capable of deciding about treatment, admission to a care facility and personal assistance services (s. 4(2)). A person is capable if they can understand the information that matters for the decision and appreciate the reasonably foreseeable consequences (s. 4(1)). The section has no age cut-off, and a diagnosis does not answer the question by itself.

Health-care decisions without a court order

If a person is found incapable of a particular treatment decision, section 20 lists who may decide, in order: a guardian of the person, an attorney for personal care, a Consent and Capacity Board representative, a spouse or partner, a child or parent, a parent with access only, a sibling, then any other relative. A parent is on the list, but a spouse or partner and any attorney for personal care rank ahead. The person deciding must follow wishes the person expressed while capable and after age 16, and otherwise act in their best interests (s. 21). If no one qualifies, the Public Guardian and Trustee decides (s. 20(5)).

Powers of attorney

A person with the capacity to give one can sign a continuing power of attorney for property or a power of attorney for personal care. Ontario says the person must be at least 18 for property and at least 16 for personal care. The tests are in the Substitute Decisions Act, 1992: s. 8 for property and s. 47 for personal care. A power of attorney stays valid if the person was capable of giving it when they signed, even if they later become incapable (ss. 9 and 47(2)). Ontario says that, for most people, having one means a guardian will not need to be appointed.

How to make a power of attorney

The person signing must be capable of giving it, and the attorney does not have to be a lawyer. Ontario says you can make one for free with its downloadable kit or a Community Legal Education Ontario web tool, or have a lawyer prepare it. It must be signed in front of two witnesses (ss. 10(1) and 48(1)). The attorney or their spouse or partner, the grantor’s spouse or partner, the grantor’s child, a person under guardianship and anyone under 18 cannot witness (s. 10(2)). A document that skips these steps is not effective, though a court can declare it effective (ss. 10(4) and 48(4)). A property attorney can act right away unless the document says it only starts if the person becomes incapable.

Courts must prefer less restrictive options

A court may appoint a guardian of property for a person incapable of managing property (s. 22) or a guardian of the person for someone incapable of personal care (s. 55). It shall not do so if the need will be met by an alternative that does not require a finding of incapacity and is less restrictive of the person’s decision-making rights (ss. 22(3) and 55(2)).

The Public Guardian and Trustee

The Office of the Public Guardian and Trustee makes financial decisions for adults found mentally incapable and acts as the substitute decision-maker of last resort for treatment and long-term care admission decisions.

ODSP trustee

The ODSP Director may appoint a trustee to help manage income support if the Director is satisfied the money is, or is likely to be, used in a way that does not benefit the recipient or their benefit unit, and no guardian of property, Public Guardian and Trustee arrangement, or continuing power of attorney for property is already acting (ODSP policy directive 10.2).

Sources (checked October 2026): Health Care Consent Act, 1996 · Substitute Decisions Act, 1992 · Ontario: Guardianship · Ontario: Make a power of attorney · Office of the Public Guardian and Trustee · ODSP policy directive 10.2, Trustees