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How this works
Section 16 of the Federal Child Support Guidelines starts from the total income on the tax return (line 15000) and adjusts it with Schedule III. This calculator applies the common adjustments, then looks up the table amount for that income. Fill in only the lines that apply to you; leave the rest blank.
Not included: employee stock options in private companies, amounts kept in a partnership or business for capital needs, prior-period self-employment reserves, and imputed income. These need a lawyer or accountant. Source: Federal Child Support Guidelines, Schedule III.
A worked example
An employee in Ontario has $85,000 on line 15000. They paid $1,100 in union dues (line 21200) and $400 in interest on an investment loan (line 22100).
- Schedule III takes both off: $85,000 − $1,100 − $400 = $83,500 of income for child support.
- For one child, the Ontario table gives $778 a month on $83,500, instead of $792 on the unadjusted $85,000.
Why line 15000 is only the starting point
Section 16 of the Guidelines says income starts with the total income on the T1 tax return, then is adjusted under Schedule III. The adjustments remove things that are not really available to support a child (union dues, employment expenses, carrying charges), avoid counting the other parent’s money twice (spousal support received from them), and replace tax figures with real ones (actual dividends instead of the grossed-up taxable amount, actual capital gains instead of the taxable half).
A court can also go beyond Schedule III. It can impute income when a parent is intentionally under-employed, has unreported income or pays themself through a company (section 19), and it can use an average of three years when income goes up and down (section 17). How imputed income works · How income is calculated.
Common questions
Is child support based on line 15000 or line 23600?
The starting point is line 15000 (total income). Schedule III of the Federal Child Support Guidelines then makes specific adjustments. Line 23600 (net income) is not used, because it subtracts things like RRSP contributions that the Guidelines do not allow.
Do RRSP contributions lower income for child support?
No. RRSP contributions are not one of the Schedule III adjustments, so they do not reduce income for child support even though they reduce income tax.
Are union dues deducted for child support?
Yes. Union and professional dues are employment deductions that Schedule III allows, so they come off line 15000.
How is self-employment income treated?
Net business income is the starting point, but Schedule III adds back capital cost allowance on real property and payments to people the parent is related to, unless they were necessary to earn the income and reasonable. A court can also impute income if expenses look too high.
