After the breakdown of a relationship in which Partner A has children from a previous relationship for whom they receive child support, many might be surprised to learn that Partner B (step-parents and those who are found to be “standing in the place of a parent (in loco parentis)) might also owe an obligation for additional child support to Partner A. This is known as “top up” child support.
Under section 3 of the Federal Child Support Guidelines, parents are presumed to pay the “Table Amount” for child support (see Leslie Taylor’s blog post on the basics of child support). A spouse who is found to be in the place of a parent for a child is subject to section 5 of the Guidelines, which gives the court discretion to determine what amount of child support is appropriate. While a spouse might protest that a support claim for children they aren’t biologically related to is unfair, it is important to remember that child support is the right of the child.
In Chartier v Chartier,  1 SCR 242, the Supreme Court of Canada made clear that:
 “The obligations of parents for a child are all joint and several. The issue of contribution is one between all of the parents who have obligations towards the child, whether they are biological parents or step-parents; it should not affect the child.”
In Vongrad v Vongrad, 2005 ABQB 52, the Court further explains:
 “The welfare of the child is the primary concern and the step-parent may be required to put the child back in the position he would have been in had the relationship not broken down. This obligation is fair since the adult chose to take on the role of becoming a step-parent and this may impose an obligation to provide a fair standard of support.”
So, how does the Court calculate top up child support? Because section 5 of the Guidelines gives the Court discretion to consider the circumstances and determine what amount is fair, there are a variety of approaches in the case law. In Friesen v Friesen, 2020 ABQB 103, the Court took a straightforward approach by determining the step-father’s Table Amount (based upon his income and the Guidelines), subtracted the amount paid by the child’s biological father, and arrived at a net amount of child support to be paid by the step-father. Importantly, this calculation was done in order to determine the amount of retroactive child support the step-father owed, showing that top up child support can be an issue not only in ongoing claims, but also in circumstances where retroactive child support is found to be appropriate.