Legal & Regulatory · Family law
Child support arrears and interest.
Arrears are unpaid support under an order or agreement. This page adds them up month by month and, if you enter a rate from your own order or provincial rules, shows what simple interest on each missed amount would look like. It never supplies a rate for you.
Arrears are the amount ordered minus what was actually paid. Whether interest is owed, and at what rate, depends on your order and provincial law, so enter your own rate or leave it at 0.
Inputs
Arrears and interest
Enter the order amount and dates, then press Calculate.
What counts as arrears
Arrears are support that was due under a court order or written agreement and not paid. Justice Canada explains that a support order can be enforced if the full amount is not being paid, that a written agreement can be enforced too, and that each province and territory runs a Maintenance Enforcement Program; to get its help the order or agreement must be registered with it. Whether the amount owing is right is a question about your order, not something this page can settle.
Interest: who decides
The sources used here do not give one national interest rule, so this guide stays with what is documented. In Ontario, the Family Responsibility Office says you use its Statement of Arrears form to claim interest on unpaid payments. It reviews the amounts against the court order, notes that interest requirements depend on when the order or domestic contract was made, and takes enforcement action on interest that accrued only because the payor did not comply with the order. Ontario publishes prejudgment and postjudgment interest rates that may apply to an order. In other provinces, ask the Maintenance Enforcement Program that holds your file.
Changed circumstances
If income changed, support may be varied, and the 2025 Federal Tables do not change an earlier order on their own. Justice Canada says a different table amount could be a change in circumstances that allows either parent to apply for a variation. Do not assume you can pay less on your own: by law you must comply with the support order or written agreement, and unpaid amounts under it are arrears.
Frequently asked questions
How do I calculate child support arrears?
Add up what the order required for each period and subtract what was paid. This page does that for equal monthly payments between two dates.
Is interest charged on child support arrears?
It depends on the order and provincial law. In Ontario the Family Responsibility Office says you use its Statement of Arrears form to claim interest owing on unpaid payments. Other provinces have their own rules.
What interest rate should I enter?
The rate stated in your order, or the rate your province publishes for your type of order. Ontario lists prejudgment and postjudgment interest rates on ontario.ca. This page does not choose one for you.
What if circumstances have changed and I cannot pay?
Justice Canada notes that sometimes people stop paying because things have changed. Stopping payment does not change the order; if the amount should change, the usual route is to ask for a variation, so speak to a family lawyer or your provincial family justice service.
Who collects unpaid child support?
Each province and territory has a Maintenance Enforcement Program. Justice Canada says that to get its help the support order or agreement must be registered with the Program.
Does the 2025 table update change old arrears?
No. Justice Canada says the updated table amounts do not automatically apply to an order made before 1 October 2025.
Sources
Verified 16 October 2026. Every rate, rule and table row used here was read on the official page listed below.
- Ontario, Family Responsibility Office: Statement of Arrears
- Ontario, Prejudgment and postjudgment interest rates
- Justice Canada, Helping with family obligations (support enforcement)
- Justice Canada, For people receiving support (Maintenance Enforcement Programs)
- Justice Canada, FAQ: 2025 update to the Federal Child Support Tables
Not legal advice
This is general information built from the published Federal Child Support Guidelines tables. It is not legal advice and it is not an official calculation. Only the table in the regulation is the legal version, and a court or agreement can set a different amount. Income for child support is defined by the Guidelines, not by your tax return alone. For an order or agreement, talk to a family lawyer, a family law information centre or your provincial family justice service.