How Is Child Support Calculated?

How Child Support Is Calculated in Canada

Canada uses the Federal Child Support Guidelines, and the core number comes from a lookup table, not a negotiation. The 'table amount' is set by three inputs: the paying parent's annual guideline income, the number of children the order covers, and the province or territory where the paying parent lives (each province has its own table to reflect provincial tax rates). For example, a payor earning $75,000 with two children pays a fixed monthly base amount straight from that province's table — the recipient's income does not change this base figure when one parent has primary care. The federal tables run up to an income of $150,000; above that, the court applies the table amount for the first $150,000 and has discretion over the percentage on the excess.

Guideline income is usually the payor's total income, but it is not always simply the top line of a tax return. For self-employed or incorporated payors, personal expenses paid through a business, retained corporate earnings, and non-arm's-length salaries can be added back — one of the most contested parts of child support. Where a parent is unemployed or under-employed by choice, or refuses to disclose, a court can impute income based on earning capacity. Full financial disclosure, typically three years of tax returns and notices of assessment plus current pay information, is mandatory.

US Models: Income Shares vs. Percentage of Income

The United States has no single national formula — each state sets its own child-support guideline, but almost all fall into one of two models. The majority of states use the income-shares model, which combines both parents' incomes, estimates what an intact family at that income level would spend on the children, and then divides that obligation between the parents in proportion to their incomes. The parent with less parenting time generally pays their share to the other. This model uses both incomes, unlike Canada's primary-care table amount, which uses only the payor's.

A minority of states use the percentage-of-income model, which applies a set percentage of the paying parent's income based on the number of children and largely ignores the other parent's income. Texas is the best-known example: its guideline generally applies 20% of net resources for one child, 25% for two, 30% for three, and so on, subject to a cap on the income to which the percentage applies. A handful of states use hybrid or older 'Melson' formulas. Because the model and the numbers differ so much between states, always confirm your specific state's guideline or official calculator.

Shared Custody, Set-Offs, and Section 7 Expenses

The base amount assumes one parent has primary care. When parenting time is shared — at least 40% of the time with each parent under section 9 of Canada's Guidelines — the calculation changes. A common approach is a set-off: each parent's table amount is calculated and the higher-earning parent pays the difference, though courts also weigh the higher overall costs of running two homes, so the set-off is a starting point rather than a fixed result. Split custody, where each parent has primary care of different children, works the same way: each parent's obligation for the children in the other's care is calculated and netted. Many US income-shares states apply their own shared-parenting-time adjustments.

On top of the base amount, parents typically share 'special or extraordinary expenses' — section 7 in Canada, and analogous 'add-on' categories in most US states. These include work-related child care, health and dental premiums and significant uninsured medical costs, post-secondary tuition, and extraordinary extracurricular activities. Crucially, section 7 expenses are usually divided in proportion to each parent's income rather than 50/50, and subsidies, tax credits, and the child's own contribution are netted out first. Because these add-ons and the base amount interact, an estimate is educational only — the binding figure should come from the official tables, a government calculator, or a family lawyer.

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