How child support is really calculated

Child support looks mechanical from the outside: find the payor's income, look up the table, done. The table is the easy part. Almost every dispute is about the inputs.

The table amount

The Federal Child Support Guidelines set a base amount using the payor's gross annual income, the number of children, and the province of residence. Where each parent has the children at least 40 percent of the time, a set-off approach applies, and the higher earner pays the difference.

Section 7 expenses

These are shared in proportion to income, on top of the table amount:

• Child care necessary for a parent to work or study
• Health insurance premiums attributable to the child
• Uninsured health expenses above a threshold — orthodontics, therapy, prescriptions
• Extraordinary expenses for primary or secondary school
• Post-secondary education
• Extraordinary extracurricular activities

The word extraordinary does real work. Ordinary activities are expected to come out of the table amount. Competitive sport with travel costs is a different matter.

Determining income

For a salaried employee this is straightforward. For someone self-employed, incorporated, or paid partly in dividends, it rarely is. Courts can add back personal expenses run through a business and can impute income where someone is intentionally underemployed or has not disclosed properly.

Retroactive claims

Support can be ordered retroactively, commonly up to three years and further where there was blameworthy conduct. The date of effective notice matters enormously — raising the issue early, even informally in writing, protects the claim.