For child support purposes in Ontario, the general rule is that a child becomes an adult at the age of majority – which is age 18 in the province.
However, the simple fact that a child has reached that age does not mean that his or her entitlement to support will automatically come to an end. This is because both the provincial Family Law Act, and the federal Divorce Act and the Federal Child Support Guidelines make provision for child support to last beyond the age of majority in some defined circumstances. Those include situations where the child remains dependent on the parents (within the meaning of the established statutory tests) or where he or she is in full time attendance at school.
The factors that go into this determination are numerous, and are tied to the unique facts of your situation. We have written an extensive article on the ins-and-outs of this question, and we recommend getting tailored legal advice as well. See “When Does Child Support Stop in Ontario” at