Child Support Calculator Ontario: What the Results Really Mean

You entered an income, picked the number of children and got a monthly figure. How much should you rely on it? A calculator can be a useful first step, but the number it gives is usually a starting point rather than a final answer.

This article explains what the result is based on, what it normally leaves out, and the situations where a court or a negotiated agreement could land somewhere else. It is general information, not legal advice.

What the calculator is actually doing

Online tools apply the child support tables. The basic child support amount depends on the number of children, the province where the paying parent lives and the paying parent's annual income. The federal "simple calculator" is the tool Ontario recommends for a rough estimate.

Simplified tables are rounded, so the official tables or the online look-up tool give the exact figure. Tables work in $1,000 brackets, and incomes between brackets are interpolated using a basic amount plus a percentage of the income over a set figure.

For children under the age of majority, the presumptive order is the table amount plus any special or extraordinary expenses. A calculator that shows only the table amount therefore shows part of that picture.

What it usually includes and what can change the result

Special expenses can include child care tied to employment, illness, disability or education, the child's share of medical and dental insurance premiums, health costs over insurance by at least $100 a year, extraordinary school costs, post-secondary costs and extraordinary extracurricular costs. Either parent can ask for them. Basic table calculators usually leave these out.

When a court may land somewhere different

• Shared parenting: if each parent has the child at least 40% of the time over a year, the court considers both parents' table amounts, the increased costs of shared care and each parent's circumstances and needs.
• Split parenting: where each parent has the majority of parenting time with at least one of two or more children, the order is the difference between the amounts each parent would otherwise pay.
• Income over $150,000: the court applies the table unless it considers that inappropriate, in which case it uses the table amount for the first $150,000 plus an amount it sets for the balance.
• Imputed income: a court can impute income as it considers appropriate, for example for intentional under- or unemployment, diverted income or unreasonable expense deductions, so a calculator using declared income may differ from a court's figure.
• Corporate income: for payers who are shareholders, directors or officers of a corporation, a court may include all or part of the corporation's pre-tax income.
• Undue hardship: a court may award a different amount if a parent or child would otherwise suffer undue hardship, subject to the standard of living comparison.
• Adult children: for a child at or over the age of majority, the court orders either the Guidelines amount as if the child were a minor, or another amount it considers appropriate.

Income, dates and which rules apply

Income is generally taken from the "Total income" sources on the T1 General, with adjustments, and a court may look at the last three years if the current figure is not the fairest measure. If your income varies, the number you type in may not be the one used.

Dates matter as well. The updated tables came into effect on October 1, 2025, and for earlier periods the 2017 tables apply. Earlier versions were 2006, 2011 and 2017, so there is no fixed update schedule. Existing orders are not automatically changed, though a different table amount may count as a change in circumstances.

Which guidelines apply also depends on your situation. The Federal Child Support Guidelines apply in divorce cases, unless both parents live in a province with its own designated guidelines, and provincial guidelines apply when parents were never married or separate without divorcing. A calculator for your province should handle this, but check which one you used.

Using the result sensibly

Treat the result as an estimate for planning and as a basis for discussion. You can arrange child support by applying online through the Child Support Service, by making a written agreement or by filing documents in court. If you apply online, the notices issued on or after October 1, 2025 use the 2025 table.

• Run the calculation with the exact annual income from your tax return and note which table the tool uses.
• Make a separate list of possible special expenses and their yearly cost.
• Count actual overnights over a year to see whether you are near 40%.
• Note anything unusual: self-employment, a corporation, recent job change or income over $150,000.
• Take your result and documents to a lawyer before agreeing to a figure or filing in court.

Frequently asked questions