“In our view, where the amount of child support that should have been paid in a prior year is under consideration, the payor’s actual income for that year is the amount that should be used to calculate support for the prior period, so long as the payor’s actual income for the prior period is known.
When calculating prospective child support, income from the previous year is used to calculate future support, essentially as a matter of convenience, because actual income for the upcoming year is incapable of exact determination. However, where, as here, the actual amount of income earned in a prior year is known, it is that amount that should determine the quantum of support that should have been paid.
Our conclusion in this regard is rooted in common sense – but also in s.2(3) of the Child Support Guidelines, SOR/97-175, which states, “[w]here, for the purposes of these Guidelines, any amount is determined on the basis of specified information, the most current information must be used.”
Further, we agree with the following comments of Baltman J. in Desjardins v. Bart, 2006 CanLII 33701 (ON S.C.) at para. 17:
Although the normal practice, based on convenience, is to address child support going forward based on the previous year’s income, once the court is intervening and looking backwards at a particular period, it makes sense to adjust child support retroactively for the relevant period, which in this case is 2004.”