What line on a tax return is used as the starting point for child support income?

Under the Child Support Guidelines, the starting point for calculating a parent's income is their total income as stated on line 15000 of the federal income tax return — previously known as line 150. This line represents total income before deductions and is the broadest income figure on a standard Canadian personal tax return.

From that starting point, certain adjustments are made under the Guidelines. Some amounts are added back (such as employment insurance benefits that a self-employed person receives, or the grossed-up portion of dividends), and some deductions are allowed (such as those listed in Schedule III). The result is the "Guidelines income" — the figure that is then matched to the provincial table to determine the monthly support amount.

Using line 15000 rather than the net income line (line 23600) means that RRSP contributions, union dues, and other personal deductions do not automatically reduce support income. This is intentional — the payor's choice to make tax-advantaged savings should not reduce the amount available to their child. Parties and lawyers will typically request each other's Notice of Assessment, which confirms the reported line 15000 figure and any amounts assessed by the Canada Revenue Agency, as the base document for any support calculation.