How is child support calculated under the guidelines in Ontario?

Child support in Ontario is calculated using the federal Child Support Guidelines, which apply to all cases involving children of separating or divorcing parents. The guidelines contain tables that set the monthly base child support amount based on two variables: the paying parent's gross annual income and the number of children to be supported.

The tables prescribe a specific monthly amount — for example, the amount a parent earning a certain income owes for one child, two children, and so on. Ontario has its own provincial table (used for separated but not divorced couples), while the federal table applies in divorce proceedings; in practice, the amounts are very similar.

In addition to the base amount, both parents typically share "special or extraordinary expenses" in proportion to their incomes. These are expenses over and above regular living costs, such as childcare required for the recipient parent to work, children's post-secondary education costs, extracurricular activities that are significant in amount, and medical expenses not covered by insurance.

Child support is the legal right of the child and cannot be waived by either parent in a separation agreement. A court will not approve a provision that deprives a child of support they would otherwise be entitled to under the guidelines.