Prejudgment and Postjudgment Interest Calculator. Simple interest under the Courts of Justice Act, at the Ministry's quarterly rates, from the day the cause of action arose to the day of the order, and from the order to payment.

What can change these figures

The rates and the quarters. The prejudgment interest rate is the bank rate at the end of the first day of the last month of the quarter preceding the quarter in which the proceeding was commenced, rounded to the nearest tenth of a percentage point; the postjudgment interest rate is the bank rate at the end of the first day of the last month of the quarter preceding the quarter of the order, rounded up to the next whole number, plus one (1) per cent (s. 127(1)). A quarter ends on March 31, June 30, September 30 or December 31. The Ministry of the Attorney General publishes the next quarter's rates after the first day of the last month of each quarter (s. 127(2); O. Reg. 339/07), and the page carries its table to the fourth quarter of 2026; a proceeding commenced, or an order made, in a later quarter has no rate here until the table is updated. The prejudgment rate does not change over the life of the claim, and the postjudgment rate does not change over the life of the judgment, however long payment takes.

The date of the order. Prejudgment interest ends, and postjudgment interest begins, on the date the order is made, even if the order is not entered or enforceable on that date or is varied on appeal, and for an order directing a reference, the date the report on the reference is confirmed (s. 127(1)). A judgment pronounced at the end of a trial and entered weeks later bears postjudgment interest from the pronouncement.

What bears no prejudgment interest. No prejudgment interest is awarded on exemplary or punitive damages, on interest accruing under s. 128 itself, on an award of costs, on the part of the order that represents pecuniary loss arising after the date of the order and identified by a finding of the court, on the amount of an advance payment for the period after it was made, where the order is made on consent (except by consent of the debtor), or where interest is payable by a right other than the section (s. 128(4)). Interest must be claimed in the pleading; s. 128(1) entitles the party "to claim and have included in the order" the award, and a statement of claim, notice of application or plaintiff's claim that does not ask for it leaves the court nothing to include.

Non-pecuniary loss in a personal injury action. The rate on damages for non-pecuniary loss in an action for personal injury is the rate the rules of court set (s. 128(2)), which is five (5) per cent per year (rule 53.10 of the Rules of Civil Procedure). The rate dates from a 1987 Law Reform Commission concern about double compensation for inflation, and the Court of Appeal has held that a trial judge who applies it without weighing the s. 130(2) factors, including changes in market interest rates, errs; in MacLeod v. Marshall, 2019 ONCA 842, at ¶¶ 45 to 56, the five (5) per cent was replaced with 1.3 per cent, the s. 128 rate of the day, and Cobb v. Long Estate, 2017 ONCA 717, at ¶ 86, says that the rates set by the court should reflect changes in market rates. The page applies the five (5) per cent as the rule provides and shows the s. 128 rate beside it so that both figures are in hand.

Motor vehicle actions. In an action for loss or damage from bodily injury or death arising from the use or operation of an automobile, no prejudgment interest is awarded under s. 128 for any period before the plaintiff served the notice under s. 258.3(1)(b) of the Insurance Act (s. 258.3(8)), and s. 128(2) does not apply to the calculation of prejudgment interest on non-pecuniary loss (s. 258.3(8.1), in force January 1, 2015), so the non-pecuniary damages bear interest at the ordinary prejudgment rate. The page runs the interest from the day you enter for the notice, where you enter one, and otherwise from the day of the accident, which overstates it.

Past pecuniary loss. Where the order includes an amount for past pecuniary loss, the interest is calculated on the total past pecuniary loss at the end of each six (6) month period and at the date of the order (s. 128(3)), so that a loss which accrued over the period does not bear interest from the first day as though it had been suffered then. The page assumes the loss accrued evenly from the day the cause of action arose to the day of the order, and gives interest on the loss accrued at each six (6) month mark from that mark to the order; where the loss was suffered on known dates, or stopped before the order, the figure differs, and a lawyer should compute it from the evidence.

The court's discretion. Where it considers it just to do so, the court may disallow interest under s. 128 or s. 129, allow it at a higher or lower rate, or allow it for a different period, taking into account changes in market interest rates, the circumstances of the case, any advance payment, the circumstances of medical disclosure by the plaintiff, the amount claimed and the amount recovered, the conduct of a party that shortened or lengthened the proceeding, and any other relevant consideration (s. 130). An appellate court interferes with that discretion only where no weight or insufficient weight was given to a relevant consideration (Stellarbridge Management Inc. v. Magna International (Canada) Inc. (2004), 71 O.R. (3d) 263 (C.A.), at ¶ 85, as applied in MacLeod, at ¶ 48). Compound interest is not awarded under ss. 128 and 129, but ss. 128(4)(g) and 129(5) let the court award interest "payable by a right other than under this section", which includes compound interest under the common law of contract damages and in equity (Bank of America Canada v. Mutual Trust Co., 2002 SCC 43, at ¶¶ 52 and 62). The page computes the statutory figures only.

Postjudgment interest. Money owing under an order, including costs to be assessed or costs fixed by the court, bears interest at the postjudgment rate from the date of the order (s. 129(1)); the base is the order, the prejudgment interest included in it and the costs, so the page adds all three (3). Where an order provides for periodic payments, each payment in default bears interest only from the date of default (s. 129(2)); where costs are assessed without an order, they bear interest from the day the party became entitled to them (s. 129(4)); an order based on an order given outside Ontario, or a foreign order filed for enforcement, bears interest at the rate, if any, of the place where it was given (s. 129(3)). Where the debtor pays in instalments, interest runs only on the balance unpaid after each payment, at the same rate; the page computes a single payment and says so.

A rate from a contract or another statute. Where interest is payable by a right other than the Act, the Act's rates give way (ss. 128(4)(g) and 129(5)). A contract rate applies as the contract provides, which may be compound or monthly rather than the simple yearly interest the page computes from the rate you entered; a rate in another statute (the Insurance Act's accident benefits, the Construction Act's holdback and lien provisions, the Employment Standards Act, 2000) applies on that statute's terms. Under s. 4 of the Interest Act (Canada), a written contract that states a rate for a period of less than a year without stating the yearly equivalent recovers no more than five (5) per cent per year.

Causes of action on or before October 23, 1989. For a cause of action arising on or before that day, the prejudgment rate is the one in the second table, the same as the postjudgment rate for the quarter (the Ministry's table; the Courts of Justice Act as it stood before the 1989 amendment), and the page uses it. For a proceeding commenced before January 1, 1985, the postjudgment rate is the prime bank rate published in the Bank of Canada Review, which the page does not carry.

The day count. The page uses the Ministry's method; namely, the amount times the rate, divided by 365, times the number of days, the days counted from the day the cause of action arose or the day of the order (excluded) to the day of the order or the day of payment (included), and leap years ignored. A court or a clerk computing to the day may count differently by a day or divide by 366 in a leap year; the difference is small and the page shows the day count so that it can be checked.

What the page does not compute. Instalment payments and the interest on each balance; compound interest, or interest under a contract that is not simple yearly interest; interest under the Insurance Act's accident benefits schedule, the Construction Act, the Family Law Act or a tax statute; interest the court has varied, disallowed or extended under s. 130; the small differences a court office's day count or rounding may produce; and the interest on an order of a court outside Ontario. Confirm the figure with a lawyer, or with the court office, before relying on it.