The Courtready Child Support Calculator implements the calculation method that follows from a careful reading of the Federal Child Support Guidelines (SOR/97-175) and the Supreme Court of Canada’s decision in Contino v. Leonelli-Contino, 2005 SCC 63. The derivation has four steps.

What counts as income

This calculator asks for each parent’s gross annual employment income, before tax, CPP, and EI deductions. The figure to enter is Box 14 of your T4 slip, or equivalently Line 10100 of your T1 General income tax return. Employment-related taxable benefits (employer-paid premiums, certain allowances) are already reported in Box 14, so do not add them on top.

The Federal Child Support Guidelines define “annual income” more broadly than employment income alone. Under FCSG s. 15, annual income for guidelines purposes is the amount on Line 15000 (Total income) of your T1 General, adjusted under Schedule III. Schedule III contains specific adjustments for self-employment business expenses, dividends (reduced from the grossed-up taxable amount to actual cash received), capital gains (reported gross rather than at the 50 percent inclusion rate), partnership income, and other items. For a parent whose only income is from a T4, FCSG annual income and T4 income are effectively the same number. For a parent with other income sources, they are not.

If you are self-employed, own a business or professional corporation, receive rental, dividend, or other investment income, or have multiple income sources, this calculator will likely understate your true FCSG annual income, and the table amount it produces will be too low. Options, roughly in order of accuracy:

• Consult a family lawyer or paralegal who can compute your guidelines income properly, including the Schedule III adjustments. If cost is a barrier, free legal clinics in your province, Pro Bono Ontario (in Ontario), and the National Self-Represented Litigants Project can sometimes help with calculations.
• Use a professional multi-field calculator that prompts for each income source separately and applies the Schedule III adjustments automatically. These tools are typically used by family law practitioners; a lawyer running a one-off consultation can use one for you.
• Compute your FCSG annual income yourself by starting from Line 15000 of your T1 General and applying the Schedule III adjustments by hand. Enter that total into the employment income field above. The field is labelled “employment income” because the dominant case is a T4 employee, but the calculator’s lookup just uses whatever number you enter; if you enter a properly-computed FCSG annual income, the resulting table amount will be accurate.
• As a rough starting point only, enter your Line 15000 figure from your most recent T1 General. This is closer to FCSG annual income than your T4 alone, but still misses the Schedule III adjustments. Treat the result as approximate.

For a mostly-T4 employee with a small amount of additional income (a few hundred dollars of bank interest, modest dividends from a non-registered account), the practical difference between T4 income and properly-adjusted FCSG annual income is often small. The FCSG table amounts change in fairly coarse income increments, so unless the additional income materially shifts your bracket, the result will be approximately right. If you are unsure, ask a lawyer.

Premise 1 — The table amount under s. 3

Section 3(1)(a) of the FCSG provides that the presumptive amount of child support is the amount set out in the applicable table for the income of the spouse against whom the order is sought, for the number of children to whom the order relates. Section 3(3)(a)(i) specifies that the applicable table is the table for the province in which that spouse ordinarily resides.

Premise 2 — Shared parenting under s. 9 (the Contino principle)

Section 9 governs cases where a child spends not less than 40% of their time with each spouse. The Supreme Court in Contino (at paragraph 49) established that the appropriate starting point in shared-parenting cases is the simple set-off between each parent’s notional s. 3 table amount. That set-off is calibrated by the further factors in s. 9(b) (increased costs of shared parenting) and s. 9(c) (conditions, means, needs, and circumstances of each spouse and child) before the final amount is fixed by the court. The set-off is a starting point only.

Premise 3 — The “applicable” number of children, from each parent’s perspective

For any given parent, the number of children to whom that parent owes support — the “applicable count” for the s. 3 table lookup — is the number of children who are NOT exclusively in that parent’s own primary care. This includes:

• Children in the other parent’s primary care (s. 3 applies; that parent is the payor), and
• Children in a shared-parenting arrangement (s. 9 plus Contino applies; both parents are payors with respect to those children)

In notation: applicable count = primary-with-other-parent + shared-parenting.

Premise 4 — The calculation

Each parent’s notional table amount is calculated using that parent’s annual income, that parent’s province of ordinary residence, and that parent’s applicable count of children. The net support payable is the difference between the two notional amounts, with the higher payor paying the difference to the lower. Where one parent’s applicable count is zero (because all children are exclusively in their own primary care), their notional amount is zero, and the calculation reduces to the standard sole-custody table amount under s. 3.

Worked example

Why this method is correct

A simpler-seeming alternative — calculating each child’s share of support separately and adding — would produce systematically higher amounts because the FCSG tables embed economies of scale for siblings. The amount for two children is less than twice the amount for one child. Using each parent’s applicable count once preserves these economies of scale exactly as the FCSG tables construct them.

What this calculator does NOT do

This calculator computes the table amount under s. 3 (or its applicable-count generalization for shared/split/mixed arrangements). It does not:

• Determine whether a child is a “child of the marriage” under s. 2 of the Divorce Act (the eligibility rule is explained in the up-front instructions, but users must apply it themselves)
• Address s. 7 special and extraordinary expenses (extracurricular, post-secondary, medical/dental, etc.)
• Apply s. 4(b) discretion at high incomes (the calculator flags where it applies; it does not estimate it)
• Apply s. 9(b)/(c) factors that may adjust the shared-parenting starting-point set-off
• Address undue hardship claims under s. 10
• Impute income under s. 19
• Calculate spousal support under the Spousal Support Advisory Guidelines (planned for a future version)

The result is a starting point for negotiation and self-representation. It is not legal advice and is not a substitute for counsel where counsel is available and accessible.

Province-specific notes

The Federal Child Support Guidelines apply nationally, but three provinces are “designated provinces” under s. 2(5) of the Divorce Act. For divorces between residents of those provinces, the applicable guidelines are their own provincial rules rather than the FCSG, even if those provincial rules in two of the three cases adopt the federal tables by reference.

Quebec

Quebec is a designated province under the Order Designating the Province of Quebec for the Purposes of the Definition “applicable guidelines” in Subsection 2(1) of the Divorce Act, SOR/97-237. For a divorce or separation between two parents who both ordinarily reside in Quebec, the applicable rules are the Modèle québécois de fixation des pensions alimentaires pour enfants, under article 587.1 of the Civil Code of Québec, and the Règlement sur la fixation des pensions alimentaires pour enfants. The Quebec model uses a different calculation method from the FCSG: it sums both parents’ incomes, derives a basic parental contribution from a Quebec-specific table, then apportions that contribution between the parents based on each parent’s share of combined income, with adjustments for custody time. This calculator does not implement the Quebec model. Quebec residents should use the Justice Québec child support calculator for intra-Quebec cases.

The Federal Child Support Guidelines (and this calculator) do apply in interprovincial Quebec cases. Where one parent ordinarily resides in Quebec and the other resides elsewhere in Canada, FCSG s. 3(3)(a)(i) provides that the applicable table is the table for the province in which the payor ordinarily resides, including Quebec when that is where the payor lives. In that scenario, the table amount produced by this calculator is correct.

Manitoba

Manitoba is a designated province under the Order Designating the Province of Manitoba for the Purposes of the Definition “applicable guidelines” in Subsection 2(1) of the Divorce Act, SOR/98-194. The applicable guidelines for a divorce between two Manitoba residents are the Manitoba Child Support Guidelines Regulation, Man Reg 52/2023, made under The Family Law Act, CCSM c F20. Section 1 of the Manitoba regulation adopts Schedule I of the federal Guidelines by reference. The dollar amount produced by this calculator is therefore correct for Manitoba residents; only the citation in a court order or domestic agreement should be to the Manitoba regulation rather than to the federal Guidelines.

New Brunswick

New Brunswick is a designated province under the Order Designating the Province of New Brunswick for the Purposes of the Definition “applicable guidelines” in Subsection 2(1) of the Divorce Act, SOR/98-256. The applicable guidelines for a divorce between two New Brunswick residents are the Child Support Guidelines Regulation — Family Law Act, NB Reg 2021-19, made under the Family Law Act, SNB 2020, c 23. Section 3 of the New Brunswick regulation adopts the federal Guidelines, so the dollar amount produced by this calculator is correct for New Brunswick residents; only the citation in a court order or domestic agreement should be to the New Brunswick regulation rather than to the federal Guidelines.

All other provinces and territories

Alberta, British Columbia, Newfoundland and Labrador, Nova Scotia, Ontario, Prince Edward Island, Saskatchewan, the Northwest Territories, Nunavut, and Yukon are not designated provinces. The Federal Child Support Guidelines apply directly to divorces between parents in those jurisdictions, and the citation in a court order or domestic agreement is to the federal Guidelines.

Sources

• Federal Child Support Guidelines, SOR/97-175 (as amended to SOR/2025-166, effective October 1, 2025)
• Contino v. Leonelli-Contino, 2005 SCC 63
• Divorce Act, RSC 1985, c 3 (2nd Supp)