Key Ontario family law terms, plainly explained.

Every Ontario decision about a child runs through the same test: what is in the best interests of the child. The Divorce Act lists the factors at section 16(3), and the Children's Law Reform Act repeats them at section 24. Both statutes work in plain language.

The factors a court weighs: the child's needs at their age and stage. The nature and strength of the child's relationship with each parent. The history of care — who actually did what during the relationship. The child's own views, weighed against their age and maturity. Family violence. The willingness of each parent to support the child's relationship with the other parent.

There is no point system and no presumption of equal time. A court looks at the specific family and weighs the factors that matter most. What counts as 'history of care' depends on what the family actually did, not on titles — a father who handled school pick-ups, homework, and weekend activities has history of care for those things, regardless of who worked outside the home.

What counts against a parent: documented family violence, a pattern of refusing to communicate or cooperate, alienation behaviour, and decisions made unilaterally that were supposed to be joint. The same test applies later if the parenting arrangement is changed.

A material change in circumstances is the threshold a court needs before it will revisit a support or parenting order. The plain-language version: a change big enough that, had the judge known about it when the original order was made, the order would probably have been different.

The everyday examples: your income is up or down by about fifteen percent or more, and not just for a month. The other parent's situation changed materially. A child becomes an adult and finishes school. Your kids start spending more time with you — enough to cross the 40% line and trigger the different child support rule covered below. The family home is sold. The spousal support clause was written to end on a particular event and the event happened.

Material change is the door; a court application is the path through it. If you and the other parent agree, the form is shorter. If you do not, the longer form starts a contested change. You can also amend a separation agreement directly if both parents sign. The clock matters either way — what you owe keeps adding up at the old amount until the new order is signed.

Child support in Ontario follows the Federal Child Support Guidelines. Below 40% parenting time, the math is straightforward: look up the paying parent's income in the table, that is the monthly amount. The other parent's income only affects how special expenses (childcare, post-secondary, big extracurriculars, health costs not covered by insurance) are split.

Once each parent has the kids at least 40% of the time, the math changes. The rule (section 9 of the Federal Guidelines) has three parts. First, you take what each parent would owe if they were the paying parent and subtract — the parent with the higher table amount pays the difference. Second, the court can adjust upward to account for the increased cost of running two homes the kids both live in. Third, the court can adjust again based on the actual circumstances of both parents and the kids. The number is rarely zero, even at exactly 50/50, because incomes differ.

Why this matters practically: moving from 35% to 40% is not just a parenting issue. It moves the support calculation onto a different track. Courts know this and look closely at whether claimed time reflects what actually happens. Overnights are the primary unit; day-time-only parenting is considered where there are no overnights.