Shared Parenting and the 40 Percent Rule for Child Support in Ontario

If your child spends close to half the time with each of you, you may wonder whether anyone pays support. The answer depends on the facts, because the court looks at several things rather than applying one formula. Shared time changes how support is calculated, but it does not switch the question off.

This article explains what the 40 percent rule is, what a court considers when it applies, and what to gather before you talk to the other parent or a lawyer. It covers Ontario and the federal rules that apply to child support.

What the 40 percent rule means

Justice Canada's guide describes shared parenting as a child spending at least 40% of the time with each parent in a year. A majority of parenting time, by contrast, means more than 60% of the time with one parent over a year.

The measure is time over a full year, not a single week or month. A schedule that looks equal in the school year may look different once holidays and summers are counted, so it helps to think about the whole calendar.

How support is set when time is shared

When each spouse has at least 40% of the parenting time with a child over a year, the court sets support by considering three things: the table amounts for each spouse, the increased costs of shared parenting arrangements, and the conditions, means, needs and other circumstances of each spouse and child.

There is no automatic formula under that rule. This is different from the usual starting point, where the basic amount is the table amount for the number of children, plus any special or extraordinary expenses. The table amount itself depends on the paying parent's income, the number of children and the province where that parent lives.

The rules described here are the federal ones used in divorce cases. The Divorce Act applies to married spouses who are divorcing, so if you were never married, or are married and not seeking a divorce, Ontario's own family legislation applies and a lawyer can confirm how it treats your situation.

A simple illustration

Suppose one child spends equal time with two parents. Under the 2025 Ontario table, monthly amounts for one child are $450 at a payor income of $50,000 and $932 at $100,000. Those figures are the amounts at the start of an income band, and amounts inside a band are slightly higher.

Comparing the two amounts is a useful reference point, because the court must consider each spouse's table amount. But it is only one of three things the court looks at, and the court is not required to simply subtract one from the other.

What can change the result

• The real parenting schedule over a year, since the 40% threshold is measured over that period.
• Extra costs created by running two homes for the child, which the court is told to consider.
• Each parent's means and needs, and the child's needs.
• Special or extraordinary expenses such as child care, health costs beyond insurance, or post-secondary education, which are dealt with separately from the table amount.
• Each parent's income, which starts from total income on the T1 General tax return and is adjusted under the Guidelines.
• A claim of undue hardship, which can lead to a different amount, though it must be denied if the claiming household would have a higher standard of living than the other.

If both parents agree on a different amount than the Guidelines would give, a court can approve it only if satisfied that reasonable arrangements have been made for the child's support. Parents cannot simply contract out of support.

What to do next

• Keep a calendar of actual parenting time for the past year, not just what the schedule says.
• Gather three years of tax returns and notices of assessment, since proof of income is needed in court.
• Remember that a parent whose income is in issue must provide personal income tax returns for the three most recent tax years.
• Note shared costs such as child care, school and activities, and what each of you pays.
• Know the forms: Form 8 sets up child support in court, Form 15 asks for a change without the other parent's consent, and Form 15D is used where both consent.
• Do not plan on the online Child Support Service, which is unavailable when parenting time is shared or split.

If the schedule changes later, a court may vary a child support order once it is satisfied a change of circumstances has occurred since the order was made or last varied. Because there is no formula, a lawyer can help you understand how your own numbers may be treated.

Frequently asked questions