Canadian family law · Child support
Shared custody child support calculator.
Check whether each parent has at least 40% of parenting time, then set off the two table amounts. This is the arithmetic starting point under section 9 of the Federal Child Support Guidelines.
Inputs
Set-off result
Enter both incomes and the parenting time split.
How is child support worked out for shared custody in Canada?
Section 9 of the Federal Child Support Guidelines applies when each spouse exercises not less than 40% of parenting time with a child over the course of a year. The amount of the order must be determined by taking into account three things: (a) the table amounts for each of the spouses; (b) the increased costs of shared parenting time arrangements; and (c) the conditions, means, needs and other circumstances of each spouse and of any child. The Guidelines do not set a formula for (b) and (c).
The calculator does part (a) only. It looks up each parent's table amount as if the other were the sole-custody parent and sets one off against the other. The difference is where many calculations start, but it is not the answer a court is required to reach.
Worked example. Ontario, 2 children, Parent A at $90,000 and Parent B at $45,000, 50/50 time. A's table amount is $1,372.00 and B's is $686.00; the set-off is $686.00 a month from Parent A to Parent B.
Frequently asked questions
What is the 40% rule for shared custody?
Section 9 applies when each spouse exercises not less than 40% of parenting time with a child over the course of a year. Below 40% for either parent, the usual table amount rule in section 3 applies.
Is shared custody child support just the difference between the two tables?
Not necessarily. The set-off covers section 9(a) only. The court must also consider the increased costs of shared parenting time arrangements and the conditions, means, needs and circumstances of each spouse and child.
What if parenting time is 50/50 and incomes are equal?
The two table amounts are equal, so the set-off is zero. Special expenses under section 7 are still shared in proportion to income.
Do I still share section 7 expenses in shared custody?
Yes, section 7 expenses can still be added and are shared in proportion to income. Use the section 7 expenses calculator for the split.
How is parenting time counted?
Section 9 uses a year's parenting time with the child. Count the days the child is with each parent over a year; this tool takes the percentage you give it.
Sources
Checked
- Federal Child Support Guidelines, SOR/97-175 (Justice Laws Website)
- Schedule I, Federal Child Support Tables (in force 1 October 2025)
The 40% threshold and the three factors are the wording of section 9; table amounts are from Schedule I. The set-off is the arithmetic of section 9(a) alone. Runs entirely in your browser. Nothing you type is sent or stored.
Not legal advice
Information only, not legal advice. Section 9 also requires the increased costs of shared parenting and each household's circumstances to be considered, so a court or agreement can land above or below the set-off shown.