Shared Parenting and Child Support: The 40% Rule Explained

Parents with near-equal schedules often hear about "the 40% rule" and assume it means child support simply cancels out. It does not, and the difference can be significant over the years a child is growing up.

This article explains what the rule says, how parenting time is counted, how the Supreme Court of Canada has said the amount should be worked out, and what to keep in mind before you agree to a schedule or a number.

Where the 40% rule comes from

Child support in BC follows the Federal Child Support Guidelines. Married parents who divorce are under the Guidelines directly, and the Family Law Act Regulation adopts the same Guidelines for support ordered under the Family Law Act, whether or not the parents were married. Our article on how child support is calculated in BC covers the usual table amount and income rules.

Section 9 of the Guidelines sets out a different approach where each parent exercises not less than 40% of parenting time with a child over the course of a year. In that case the amount must be determined by taking into account three things:

• The table amounts for each parent, based on each parent's income.
• The increased costs of shared parenting arrangements, since two homes usually cost more than one.
• The conditions, means, needs and other circumstances of each parent and of each child for whom support is sought.

How parenting time is counted

Forty percent of a year is 146 days. The Guidelines do not say how those days are to be counted, and the counting method is a common source of disagreement. Parents may count overnights, full days or hours, and they often disagree about who is credited with time when the child is at school, at daycare or asleep.

Example (illustration only): a schedule of alternate weekends from Friday to Monday morning (about 78 overnights a year) plus every Wednesday overnight (52 more) gives roughly 130 overnights, or about 36%. Add 14 more overnights over the summer and the total rises to about 144, still just under 40%. Small changes in the schedule, or in the counting method, can move a family across the line.

The test looks at the whole year, so a month of extra time does not settle it. Keeping an accurate calendar of the time each parent actually has the children is one of the most useful things you can do if the 40% question may come up.

Set-off is the starting point, not the answer

The Supreme Court of Canada set out the approach in Contino v. Leonelli-Contino, 2005 SCC 63. The Court held that once the 40% threshold is met, a simple set-off of the two table amounts is a starting point under section 9(a), but the court must go on to consider the increased costs of shared parenting under section 9(b) and the parents' and child's circumstances under section 9(c). The Court said there is no presumption in favour of the ordinary table amount once section 9 applies, and that budgets and evidence of actual spending matter.

Example (illustration only, not actual table figures): if the table amount for one parent's income is $900 a month and for the other parent's income is $500 a month, the simple set-off is $400 a month payable by the higher earner. A court could then adjust that figure up or down after looking at which parent carries more of the children's costs, such as clothing, activities and housing, and at the gap between the two households' incomes and standards of living.

Special expenses are still shared

Section 7 of the Guidelines covers special or extraordinary expenses, such as child care needed for a parent's work, health costs above insurance, some education costs and extraordinary extracurricular activities. These are handled separately from the section 9 amount. The guiding principle in section 7(2) is that these expenses are shared in proportion to the parents' incomes, after deducting any contribution from the child.

Agreements, changes and the children's interests

Parents can agree on child support. Under the Family Law Act, an agreement about child support is binding only if it is made after separation or when the parties are about to separate, and a court may set aside or replace it if it would make a different order under the Guidelines-based approach in section 150. A figure that ignores the Guidelines can be reopened later.

If the schedule changes in practice, the support agreement or order does not change on its own. It has to be changed by a new agreement or a court order, so it is worth dealing with that promptly.

Finally, the schedule itself should be about the children, not the support calculation. Parenting arrangements are decided on the children's best interests, as our article on whether 50/50 parenting is the default in BC explains. A schedule built to reach or avoid 146 days is likely to be questioned.

Sharing parenting time? Get the support numbers checked before you agree

Our family lawyers can review your schedule and the time records, work through the section 9 factors with you, and prepare or review a child support agreement.

Call 604-259-2844 or send us a message to arrange a consultation at our Vancouver office.