Can my ex quit her job to lower child support in Ontario?

No, not successfully. A parent who quits a job or deliberately earns less to change child support can have income imputed — treated by the court as still earning what they could earn. Section 19 of the Federal Child Support Guidelines, the federal rules Ontario uses to set child support, exists to stop exactly that move.

Child support is built on the payor's income. So the tactic only matters when the parent who pays support is the one cutting their income. If your ex pays you and she quits to shrink the cheque, the court can look straight through it. The same rule can apply to you. If you leave a job and the court decides you did it to pay less, it can set support on the income you walked away from.

When this does apply

A court imputes income — assigns a higher figure than the parent reports — when the low income looks intentional. Section 19(1) of the Guidelines lists the triggers. The common ones for separated parents:

1. A parent is intentionally unemployed or underemployed with no health, childcare, or reasonable-education reason.
2. A parent switches to lower-paid work right around the time support is set or reviewed.
3. A parent hides income — unreported cash, or money routed through a corporation.
4. A parent will not disclose the documents the court needs to see the real number.

Concrete version: your co-parent earns $90,000, quits the week before the support motion, and files as a job seeker with no health or caregiving reason. A court can set support as if she still earns $90,000. The timing and the missing reason are what sink it.

When this doesn't apply

Imputing income is not a punishment for earning less. It needs intent. A genuine layoff, a real career change to comparable work, retraining that lifts future income, a health condition, or staying home with a child too young for care are all reasonable, and a court usually accepts the lower income. Steps to Justice sets out the same reasonable-cause line in plain language.

If your own income dropped for a real reason, you do not wait to fight an imputation — you bring the change forward yourself. A lasting income change is a material change in circumstances, the test for changing a child support order.

What to do

Pick the situation you are in and act on it.

If you suspect your ex is underearning to move the number: gather the proof (her qualifications, work history, the timing of the change, and jobs she could fill), then bring a motion to impute income. A judge decides on evidence, not suspicion.

If you are the payor and your income genuinely fell: document the reason the day it happens, the layoff letter or the medical note, keep paying the current order until a court changes it, and apply to vary it. Run your realistic number on the free calculator against the federal tables first, so you know what you are asking for. For the full formula, see how child support is calculated and how shared custody changes the number.

Run the free calculator at cairnguide.ca/calculator.