How is child support calculated in Ontario?

TL;DR. Child support in Ontario is calculated using the Federal Child Support Guidelines — a table indexed to the payor's gross annual income and the number of children. One income earner of $100,000 with two children pays about $1,416 per month in basic table support. Section 7 of the Guidelines adds a proportional share of "special expenses" — childcare, certain medical costs, post-secondary, and extraordinary extracurriculars — on top of the table. Shared parenting (where each parent has the children at least 40% of the time) changes the formula under section 9. Above $150,000 of payor income, the table is the starting point and courts can adjust. Child support is the right of the child, not the parents — you cannot agree to less than the table without judicial scrutiny. This article walks you through each piece, with the example numbers.

Why this matters

Most of the anxiety about child support is anxiety about the unknown. The number feels like it could be anything. In practice it cannot. Ontario's child-support number for the vast majority of separated fathers is determined by two inputs — your gross income and the number of children — and a published table the federal Department of Justice updates periodically. Two minutes with the table will tell you the rough number. Two minutes with the Cairn calculator will tell you the specific number, including the tax adjustment and what actually hits your account each pay period.

The rest of this article is about understanding what the table includes, what it does not, and the three situations where the formula moves: section 7 special expenses, shared parenting, and incomes above $150,000.

What are the Federal Child Support Guidelines?

The Federal Child Support Guidelines are a federal regulation that sets out how child support is calculated in Canada. Ontario adopted the federal Guidelines for all parents — married, divorcing, or unmarried — through Ontario's Child Support Guidelines. The two regulations are aligned, with one or two Ontario-specific tweaks that rarely matter in practice.

The core rule of the Guidelines: the payor parent owes the "table amount" set out in Schedule I, based on their gross annual income and the number of children. The receiving parent's income does not factor into the table amount for basic support — only into section 7 special expenses and, in shared-parenting cases, the section 9 calculation.

A few definitions to lock in before reading further. The "table amount" is the monthly basic support figure from the federal table for Ontario. "Gross annual income" is your total income from all sources before tax, calculated under section 16 of the Guidelines — usually your line-15000 income from your most recent T1 General, with adjustments for things like self-employment add-backs and trust distributions. "Special expenses" are the section 7 categories, shared on top of the table in proportion to the parents' incomes. "Shared parenting" is parenting time at or above the 40% threshold per parent, which triggers the section 9 calculation.

The Guidelines are mandatory. The amount they generate is presumed correct. Parents cannot agree to less than the table amount in a separation agreement without a court reviewing the agreement and finding that the lesser amount is in the children's best interests. Child support is the right of the child — neither parent has the authority to bargain it away.

How does the federal table actually work?

Open the federal table for Ontario. Find your income row. Find your column for number of children. The cell is your monthly basic support amount. That is the calculation in the typical case.

Income	1 child	2 children
$60,000	$549/mo	$898/mo
$80,000	$722/mo	$1,176/mo
$100,000	$896/mo	$1,416/mo
$150,000	$1,330/mo	$2,084/mo

Example numbers to make this concrete:

• $60,000 income, 1 child: $549/month
• $60,000 income, 2 children: $898/month
• $80,000 income, 1 child: $722/month
• $80,000 income, 2 children: $1,176/month
• $100,000 income, 1 child: $896/month
• $100,000 income, 2 children: $1,416/month
• $150,000 income, 1 child: $1,330/month
• $150,000 income, 2 children: $2,084/month

(Figures from the November 2017 federal tables for Ontario, which remain in force.)

$1,416/mo at $100K, 2 children

Two things to note. First, the table amounts are after-tax in the payor's hands — child support is not tax-deductible to the payor and not taxable to the recipient. This is a significant departure from the pre-1997 rule and from the spousal-support rule. Plain English: $1,416 of child support actually moves $1,416 from your account to hers. There is no T1213 equivalent and no paycheque adjustment. The number is the number. For the gritty detail on table usage including how to handle income changes and tax-year updates, see Federal Child Support Tables explained.

Second, the table only handles basic support. The section 7 special expenses sit on top of it. The next section explains how those work.

What are section 7 special expenses?

Section 7 of the Federal Child Support Guidelines lists six categories of "special or extraordinary expenses" that are paid on top of the table amount in proportion to the parents' incomes:

1. Childcare expenses incurred because of the receiving parent's employment, education, or other necessary activity
2. Medical and dental insurance premiums attributable to the child
3. Health-related expenses exceeding insurance coverage by at least $100 per year — orthodontics, prescription drugs, mental-health services, physiotherapy
4. Extraordinary educational expenses for primary or secondary school, including tutoring
5. Post-secondary education expenses
6. Extraordinary extracurricular activities

Each category has its own test. Childcare and medical premiums are typically straightforward. The "extraordinary" categories — education and extracurriculars — require a two-part test: necessary in relation to the child's best interests, and reasonable in light of both parents' incomes.

The math is proportional. If your income is $100,000 and her income is $50,000, your combined income is $150,000 and your share is two-thirds. A $6,000 section 7 expense means you pay $4,000 and she pays $2,000. The Guidelines also require deducting any contributions, subsidies, or tax credits available to the receiving parent before splitting.

A clean example: childcare costs $1,200 per month, the Canada Child Benefit and childcare expense deduction reduce the net cost to $720, your proportional share is 67%, so your section 7 contribution to childcare is roughly $482 per month — on top of the table amount.

For the full breakdown of each category and the proportional math, see section 7 special expenses. The reason this matters: men often look at the table amount and budget around it, then get blindsided by a $400-to-$800 monthly section 7 number they did not anticipate. The fix is to model both together from the start. The Cairn calculator does this in one screen.

How does shared parenting change the calculation?

Where each parent has parenting time of at least 40%, section 9 of the Guidelines applies. The calculation is different. There are three considerations under section 9:

1. The amounts each parent would pay under the table for their income
2. The increased costs of shared parenting arrangements (two homes, duplicated equipment, transportation)
3. The condition, means, needs, and other circumstances of each parent and any child

The starting point in practice is the "set-off" approach — each parent's table amount is calculated, and the higher earner pays the difference. Example: payor income $120,000 with 2 children, table is $1,653; recipient income $70,000 with 2 children, table is $1,033. The set-off is $1,653 - $1,033 = $620/month payable from the higher earner.

The set-off is not the whole story. Section 9 explicitly permits courts to depart from it where the set-off would leave a parent unable to meet the children's needs, or where the duplicated costs of two households justify a different number. In practice, courts often start from the set-off and adjust modestly upward. Going significantly below the set-off requires a strong case.

A practical note worth knowing: the 40% threshold is calculated over the year, not week by week. A parent who has the children every other weekend and one weeknight is typically around 25-30% — below the threshold, so the regular table applies. A parent with a 5/9 or 6/8 schedule is often above the threshold. The line between is not always obvious; section 9 applications are one of the most heavily litigated questions in Ontario family law. The full breakdown is in how shared parenting changes child support in Ontario.

A repeated warning from the previous pillar that bears repeating here: do not game the parenting-time split for the section 9 outcome. Judges have seen every version of it.

What happens above $150,000 of income?

Above $150,000 of payor income, the table amount for the first $150,000 of income still applies, but the amount for income above the threshold is discretionary under section 4 of the Guidelines. Courts can apply the table to the additional income, or set a different amount based on the children's "condition, means, needs and other circumstances" and the financial ability of each spouse to contribute.

In practice, the most common outcome at higher incomes is the table amount applied to the full income — at the upper income range the table levels off, meaning each additional $10,000 of income adds proportionally less to the support amount. Courts only deviate where the table would produce a result clearly disproportionate to the children's actual needs.

The drift can be significant for very high earners — incomes above $500,000, where the table would imply support amounts that don't track to real child-rearing expenses. For most men with incomes in the $150,000-$300,000 range, the table amount is the answer, with section 7 expenses on top. The Cairn calculator handles incomes through this range with the right treatment.

When does child support change?

Child support is not a one-time number. It updates when the underlying inputs change. Three triggers matter most.

Income change. Either parent's annual income change triggers a recalculation. The Guidelines do not require a court order for this — most agreements include an annual exchange of T1 General returns and Notices of Assessment by a fixed date (typically June 1) and a recalculation effective the following month. If your income drops materially during the year — job loss, illness, business income decline — you can apply to vary support based on the new income, but the change is not automatic. If a parent deliberately earns less to lower support, the court can impute income. Continue paying the existing amount until a new one is agreed or ordered, then claim the variation back to the date of the application.

A child turning 18. Child support continues past 18 only if the child is a "child of the marriage" — meaning still dependent because of full-time education, illness, or disability. The most common case is full-time post-secondary, which keeps the child support obligation active typically through the completion of a first undergraduate degree. The table amount may be adjusted where the child is living away from home, and the child may be expected to contribute from their own earnings or student loans.

A material change in parenting time. A shift from primary to shared parenting — or vice versa — triggers a recalculation. The 40% threshold is the line.

Two things courts will not entertain. First, using child support as a tool to punish the other parent for the breakup. Second, "we agreed she would take less" if the agreed amount is below the Guidelines and not in the children's best interests. Both arguments fail every time they are made.

The one thing to do this week

Run the Cairn calculator. Enter your two numbers — gross income and parenting structure — and your children's ages. You will have the table amount, an estimate of section 7 obligations, and the cash-flow picture in two minutes. The number it gives you is not legal advice, but it is the same number a paralegal will quote in your first meeting. Walk in knowing it.

Where Cairn helps next

This article gives you the framework. The free calculator turns it into your specific numbers — what you'd actually pay each month, what would hit your account every two weeks. No email. No account.

• Your real Ontario support numbers in two minutes
• The cash-flow comparison with and without a tax adjustment
• A six-page PDF report you can email to yourself
• 14-day money-back promise if you take it further into a paid plan

Run the free calculator →

The what we do page lays out scope — Ontario only, information not legal representation. For the spousal-support side of the math, our pillar on spousal support in Ontario is the next read.