When we calculate a parent's income, our starting point is usually last year's total income as reported at line 15000 of that parent's Income Tax Return (formerly line 150). However, there are many adjustments which can be made from there, which is why we refer to a parent's income for child support purposes as their guideline income.

However, if circumstances have changed, we need to instead use actual current income (Lavergne v Lavergne, 2007 ABCA 169 at paras 17, 18, 22; Martens v. Martens, 2016 ABCA 107). We may also use a reasonably accurate estimate and then retroactively adjust or top-up at the end of the year once actual income is known (Lavergne v Lavergne, 2007 ABCA 169 at para 22).

If income fluctuates (for example if someone is self-employed or paid in commission), and using the previous year's income wouldn't be the fairest method, then we may use a three-year average.

Union/professional dues must be deducted from income.

There are many adjustments that are set out at Schedule 3 to the Federal Child Support Guidelines: https://www.CanLII.org/en/ca/laws/regu/sor-97-175/latest/sor-97-175.html#SCHEDULE_III__3838897

Child support is recalculated on an annual basis, or whenever there is a material change in circumstances. Child support orders, including Divorce Judgments, will require that parents exchange Income Tax Returns, Notices of Assessment/Reassessment, and for newer orders, specific documentation relating to businesses/trusts by June 30th of each year. Read more about Exchanging Financial Documentation.

In some circumstances, we might set a person's guideline income at a higher amount, which is referred to as Imputing Income. This is usually to adjust for tax rates, where they're self-employed and benefit from business deductions, or where they're avoiding child support such as by working for cash that they're not reporting.

There are many adjustments which we apply to Self-employment Income.