Note: this tool provides a general, informational estimate only. Applicable rates and rules can change, and your actual entitlement depends on the specific terms of your judgment — treat any estimate as a planning aid, not a final number.
What postjudgment interest is
Postjudgment interest is interest that can accrue on the amount awarded in a judgment, starting from the date of the judgment itself, for as long as it remains unpaid. The idea is the same one behind prejudgment interest: money you're owed and haven't received loses value over time, so interest compensates for the ongoing delay.
How this differs from prejudgment interest
Prejudgment interest covers the period before a decision is made — from when the loss happened or the debt became due, up to the date of judgment. Postjudgment interest picks up from exactly that point forward, covering the period after judgment for as long as the debtor hasn't paid. Together, they can cover the entire span from the original loss through to actual payment.
It also helps to keep these two stages conceptually separate rather than blending them together. Exactly what base amount postjudgment interest applies to — the original principal alone, or a broader figure that also reflects prejudgment interest and costs — depends on the specific terms of your judgment, so confirm that detail directly from the judgment itself rather than assuming either way.
How it's generally calculated
Like prejudgment interest, postjudgment interest in Ontario is generally governed by the Courts of Justice Act framework, with an applicable rate that's set and updated periodically rather than fixed indefinitely. Because the current rate can change, this guide doesn't quote a specific percentage — confirm the current rate before relying on any calculation for your actual situation.
Confirm the current rate
The postjudgment rate is set under the same general framework as prejudgment interest but is calculated separately and can differ from it. The calculator above is intended to use current figures — always double check against the actual judgment terms for your case.
What you'll need to use it
- The date of your judgment.
- The amount awarded, including any prejudgment interest and costs the judgment already includes.
- How much (if anything) has been paid since, and on what date(s).
- Today's date, or the date you want to calculate interest up to.
Having these on hand, ideally sourced directly from your written judgment rather than memory, makes the calculator's output far more reliable — and gives you a documented basis to point to if the figure is ever questioned.
Why it matters for enforcement
Postjudgment interest is one of the more overlooked parts of collecting on a judgment. Because it accrues automatically over time, the amount actually owed can grow well beyond the original judgment figure the longer enforcement takes — which is one more reason not to let enforcement drift indefinitely. It also means any partial payment should be tracked carefully, since it affects the base amount interest continues to accrue on. See judgment enforcement for the practical side of collecting what's owed.
From the debtor's side, this cuts the other way: the longer payment is delayed, the more the total obligation grows. Some debtors aren't aware of this until it's pointed out, and it can be a legitimate, factual reason to encourage prompt payment rather than continued delay — worth mentioning plainly rather than assuming it's already understood.
A worked example (illustrative)
To show the mechanic only — not the actual current rate — say a judgment for $5,000 remains entirely unpaid for exactly one year, and purely for illustration, assume a hypothetical annual rate of 3%. Simple interest would be calculated as $5,000 × 0.03 × 1 year = $150, making the total owed $5,150 at that point, before accounting for any further time or enforcement costs. Your actual rate and amount will differ — confirm the current figures separately.
Situations that make the math trickier
A judgment paid in full, all at once, shortly after it's made is the simplest case — a short period, a single calculation, done. Real enforcement is often messier:
- Multiple partial payments over time. Each payment changes the base amount interest accrues on from that point forward, which means the calculation needs to be broken into segments rather than done as one single stretch.
- Payments through a payment plan. If the debtor is paying gradually under an agreed schedule, interest calculations need to track the declining balance accurately over the life of the plan.
- A judgment that includes costs awarded separately. Depending on how costs were awarded, they may or may not accrue interest in the same way as the principal judgment amount — this is worth confirming rather than assuming either way.
In any of these situations, breaking the timeline into clearly dated segments — this amount, from this date to that date — keeps the calculation manageable and accurate, even if it takes a few separate steps rather than one simple formula.
If the debtor disputes your calculation
If a debtor questions the interest amount you're claiming, be ready to prove your case: the judgment date and amount, every payment and its date, and the rate you applied at each stage. A clear, dated breakdown is far more persuasive — and far harder to dispute credibly — than a single final number presented without support.
Keeping track as time passes
If enforcement takes months or longer, keep a simple running record: the original judgment date and amount, any partial payments and their dates, and the date you last calculated interest. This makes it far easier to state an accurate, up-to-date total if you need to update an enforcement filing or respond to a partial payment offer, rather than recalculating everything from scratch each time.
Common mistakes to avoid
- Forgetting postjudgment interest exists and only tracking the original judgment amount.
- Using an outdated or guessed rate instead of confirming the current one.
- Not adjusting the calculation after a partial payment, which changes the base amount going forward.
- Confusing postjudgment interest with prejudgment interest, which cover different periods and are calculated separately.
- Losing track of dates needed to recalculate interest accurately later.
Official sources
- Courts of Justice Act, R.S.O. 1990, c. C.43 — sets the Small Claims Court’s jurisdiction and the statutory framework for pre- and post-judgment interest.
- ontario.ca: Suing Someone in Small Claims Court — the official overview, including the current monetary limit.
Frequently asked questions
Does postjudgment interest apply automatically?
Generally, yes — unlike prejudgment interest, which you typically need to specifically claim, postjudgment interest generally applies automatically to an unpaid judgment under the applicable framework.
What if the debtor pays part of the judgment?
A partial payment generally reduces the amount interest continues to accrue on going forward — keep a clear record of the payment date and amount to calculate this accurately.
Does the postjudgment rate change over time?
The applicable rate can be set based on conditions at the time of judgment, or can be updated periodically depending on the framework in place — confirm the current rules rather than assuming a rate stays fixed indefinitely.
Can I include postjudgment interest when I try to enforce the judgment?
Yes — when pursuing enforcement, it's generally appropriate to include accrued postjudgment interest in the total amount you're seeking to collect, not just the original judgment figure.
Is postjudgment interest compound or simple?
It's generally treated as simple interest rather than compounding, similar to prejudgment interest, though it's worth confirming against your specific judgment terms.
Does interest stop if I stop actively pursuing enforcement?
Generally, no — postjudgment interest continues to accrue based on the judgment remaining unpaid, regardless of whether you're actively taking enforcement steps at any given moment.
What if I don't know the exact date the debtor made a payment?
Use your best documented estimate — a bank record, receipt, or dated communication — rather than guessing. If the exact date is genuinely unclear, note that uncertainty rather than presenting an estimate as if it were confirmed.