Short answer: Ontario child support starts with a table amount based on the paying parent's annual income and the number of children. Special or extraordinary expenses, such as child care, are then shared in proportion to both parents' incomes. Different rules apply when parenting time is shared at least 40 percent each.
The rules that apply
Child support for divorcing spouses is set under the Federal Child Support Guidelines. For unmarried parents and separated spouses who are not divorcing, Ontario's Child Support Guidelines apply. The two sets of rules work the same way and use the same tables, so the calculation is the same in almost every case.
The tables were updated on October 1, 2025 to reflect more recent tax rules. The update does not automatically change an order made before that date, but a difference in the recalculated amount can be treated as a change in circumstances.
Step 1: the table amount
The base amount comes from the table for the province where the paying parent lives, using that parent's annual income and the number of children the support is for. For incomes over $150,000, the table sets a formula for the amount above that level, and a court can depart from it in limited cases.
Step 2: special or extraordinary expenses
Section 7 of the guidelines adds certain expenses on top of the table amount, shared in proportion to the parents' incomes after tax considerations. These can include:
- child care needed for a parent to work or study
- the portion of medical and dental insurance premiums for the child
- health related expenses over $100 a year not covered by insurance
- extraordinary expenses for primary or secondary school education
- post-secondary education expenses
- extraordinary extracurricular activity expenses
The expense has to be necessary in the child's best interests and reasonable in light of the family's means and spending before separation.
Shared and split parenting
- Shared parenting. Where each parent has the child at least 40 percent of the time over a year, section 9 applies. Courts usually start by offsetting the two table amounts, then look at the increased costs of shared parenting and each household's means.
- Split parenting. Where each parent has primary care of at least one child, each pays the table amount for the child or children with the other, and the amounts are offset.
How income is decided
Income starts with the total income line on the parent's tax return, with adjustments under the guidelines. Disputes often arise where a parent is self-employed, earns cash or dividends through a corporation, has a large bonus one year, or is earning less than they could. In those cases a court can impute income, meaning it sets support based on the income the parent should reasonably be earning.
Undue hardship and adult children
Either parent can ask the court to change the amount because of undue hardship, for example unusually high debts or support obligations to other children, but the bar is high. Support can continue past age 18 while a child is in full-time education or cannot become independent for another reason, such as illness or disability.
Getting it in writing
Child support can be set in a separation agreement, a court order or, in some cases, through Ontario's online child support service. Support is the child's right, so parents cannot simply agree to waive it. Read our guide to separation agreements in Ontario for what else the agreement should cover.
Frequently asked questions
How much is child support in Ontario for one child?
It depends on the paying parent's income. The federal table for Ontario sets the monthly amount for each income level, and special expenses are added on top.
Is child support based on gross or net income in Ontario?
On gross income, starting with the total income line of the tax return, adjusted under the guidelines.
What is the 40 percent rule for child support?
If each parent has the child at least 40 percent of the time over a year, the shared parenting rules apply, usually starting with an offset of the two table amounts.
Does child support stop at 18 in Ontario?
Not automatically. Support can continue while the child is in full-time education or cannot become independent for another reason.
Did the child support tables change?
Yes. Updated federal child support tables took effect on October 1, 2025. Existing orders do not change automatically, but the update can support a request to recalculate.
Can parents agree to no child support?
Not validly. Child support belongs to the child, and a court can set support even if the parents agreed to none.
Talk to our team
This guide is general information, not legal advice. For advice on your situation, see our family lawyer in Toronto page. To book a paid consultation (30 minutes, $150 plus HST, paid when you book), book online or call (647) 271-1646. The phone is answered 24 hours a day, 7 days a week, and office meetings are by appointment. Civitas Law is a team of legal professionals under the leadership of lawyer Nasibeh Mehrpouyan, serving clients in English, French, Farsi, Russian and Serbian.