Does child support change when parents share custody equally in Ontario?

Yes. When each parent has the child at least 40 percent of the time (the threshold for "shared custody" under the Guidelines), the standard table calculation does not automatically apply. Instead, the court has discretion to set an amount that accounts for the increased costs each parent bears from caring for the child in their own home.

Courts usually start by calculating what each parent would pay if they were the payor, then offset those amounts — the parent who earns more typically pays the difference to the lower-earning parent. However, a simple set-off is not always the result. The court also considers the actual spending patterns, the standard of living in each household, and what best serves the child's financial interests. A judge can adjust the set-off amount up or down.

The 40 percent rule is calculated across the full year, not just on a weekly schedule. Holidays, summer stays, and extended visits all count. If your parenting plan is near the threshold, precise record-keeping matters. A lawyer can help you model the likely outcome for your specific income levels and parenting schedule before you negotiate or attend court.