Prejudgment Interest Rules in Washington
At a glance
| Governing law | Washington splits this across two different bodies of law. RCW 4.56.110 governs interest on the JUDGMENT itself, running from the date of entry (or verdict), and sets different rates for written-contract judgments, tort judgments against public agencies, tort judgments generally, and a residual catch-all tied to the usury statute, RCW 19.52.020. Separately, a judge-made common-law doctrine (Mall Tool Co. v. Far West Equipment Co.; Prier v. Refrigeration Engineering Co.) creates the actual right to TRUE prejudgment interest, running before suit is even filed, on a claim, of any type, that is 'liquidated.' That doctrine borrows its default rate from the general legal-rate-of-interest statute, RCW 19.52.010 (12%) |
|---|---|
| Interest rate | For a true prejudgment award on a liquidated claim: the rate the parties agreed to in writing, or ordinarily 12% per year under RCW 19.52.010 if there's no agreed rate; medical-debt prejudgment interest is capped at 9%. For a written-contract judgment generally: the contract's own specified rate (RCW 4.56.110(1)). For an ordinary tort judgment (which draws interest only from the date of entry, not before, under RCW 4.56.110(3)): 2 percentage points above the prime rate for a private defendant, or 2 points above the 26-week Treasury bill yield for a 'public agency' defendant. Judgments not covered by RCW 4.56.110(1)-(5) use the maximum rate permitted under RCW 19.52.020 |
| When interest starts running | For a liquidated claim, interest runs from the date the debt became due, the date payment should have been made, not from the date suit was filed or judgment entered; this is Washington's true prejudgment period. For an ordinary tort judgment under RCW 4.56.110's general rules, by contrast, interest runs only from the date judgment is entered (or from the date of a jury verdict, if a judgment on that verdict is later affirmed on review), there's no earlier accrual for that claim type under the statute |
| Contract vs. tort claims | Washington's operative distinction is liquidated versus unliquidated damages, not contract versus tort. A claim of either type earns true prejudgment interest if its amount can be computed with exactness from the evidence, without resort to a judge's or jury's opinion or discretion, this doctrine has been applied to a tort claim (the cost of repairing a negligently designed ice rink, held liquidated once the repair contracts were let) just as readily as to a contract debt. An unliquidated claim, most personal injury verdicts, and any contract claim whose damages require expert testimony or discretion to fix, gets no true prejudgment interest; the judgment only starts drawing interest from the date of entry under RCW 4.56.110's general rules |
| Mandatory or discretionary | For a liquidated claim, prejudgment interest is essentially automatic once the claim qualifies: courts don't have discretion over WHETHER to award it, only over the antecedent question of whether the claim actually IS liquidated. For an unliquidated claim, there's no discretionary judicial power to award true prejudgment interest at all under Washington's doctrine; the claim simply doesn't qualify, and interest instead starts from the date judgment is entered under the general statute |
| Simple or compound | Neither RCW 4.56.110 nor RCW 19.52.010 mentions compounding; both describe a straight annual rate applied to a principal sum, and Washington courts and practitioners apply it as simple interest |
| Claims against the government | Washington doesn't bar prejudgment or post-entry interest against the government, but it does set a different, generally lower RATE for a tort judgment against a 'public agency' (state agencies, counties, cities, school districts, and similar political subdivisions defined in RCW 42.30.020): 2 points above the 26-week Treasury bill yield, instead of the 2-points-above-prime rate that applies to a private tort defendant. This is a rate difference, not a bar: a liquidated claim against a public agency can still draw true prejudgment interest under the same common-law doctrine that applies to a private defendant |
| Other exceptions | Medical-debt prejudgment interest is capped at 9% under RCW 19.52.010(2). The tort and residual-catch-all rates are pegged to published financial benchmarks reset monthly, so the specific rate depends on the judgment-entry month. When a liquidated claim faces an opposing unliquidated counterclaim, Washington generally calculates prejudgment interest on the liquidated amount before the offset. ESSB 5993 would have reduced medical-debt interest to 1%, but the 2026 session adjourned after the bill returned to Senate Rules without final passage |
Requirements one by one
Governing law
Two different bodies of law work together here. RCW 4.56.110 is the general "interest on judgments" statute: it sets the rate that applies once a judgment is entered, and for most judgment types that's also when the interest clock starts. Separately, Washington courts have long recognized a common-law right to TRUE prejudgment interest, interest that starts running before the lawsuit is even filed, on a claim that is "liquidated." That doctrine, traced through cases like Mall Tool Co. v. Far West Equipment Co. and Prier v. Refrigeration Engineering Co., borrows its default rate from the state's general legal-rate-of-interest statute, RCW 19.52.010, rather than from RCW 4.56.110 itself.
Interest rate
If your claim is liquidated and qualifies for true prejudgment interest, the rate is whatever the parties agreed to in writing, or ordinarily 12% per year under RCW 19.52.010 if there's no agreed rate. Medical debt is the express exception: subsection (2) caps its prejudgment interest at 9%. Once a judgment is entered, RCW 4.56.110 takes over for interest going forward: a written-contract judgment carries the contract's own specified rate; an ordinary tort judgment against a private party carries 2 points above the prime rate (reset monthly); a tort judgment against a "public agency" carries 2 points above the 26-week Treasury bill yield instead; and a judgment outside subsections (1) through (5) uses the maximum rate allowed under RCW 19.52.020.
When interest starts running
For a liquidated claim, the clock starts on the date the debt became due, the date it should have been paid, which can be well before the lawsuit was filed or the judgment entered. That's Washington's actual prejudgment period. For an ordinary tort claim under the general judgment-interest statute, there's no such earlier start date: interest runs only from the date the judgment is entered, or, if a case goes to a jury and the judgment on that verdict is later affirmed on appeal, from the date the verdict itself was rendered.
Contract vs. tort claims
The dividing line here is liquidated versus unliquidated damages, not the legal label of the claim. Washington's courts have applied the liquidated-damages interest rule to a tort claim as readily as to a contract claim: in one case, the cost of repairing a negligently designed ice rink was held to be a liquidated sum once the repair contracts were finalized and the cost became fixed, even though the underlying claim sounded in tort. What matters is whether the amount can be computed with exactness from the evidence, not whether the theory of liability is contract or tort. An unliquidated tort verdict (most personal injury cases) and an unliquidated contract claim (one requiring expert testimony or judicial discretion to value) are treated the same way: no true prejudgment interest, just ordinary interest from the date of entry.
Mandatory or discretionary
For a liquidated claim, awarding prejudgment interest isn't left to a court's discretion, once the claim qualifies as liquidated, interest follows as a matter of course. The real discretion, if any, is exercised earlier, in deciding whether the claim actually meets the liquidated-damages test. For an unliquidated claim, courts have no discretionary power to award true prejudgment interest at all under this doctrine, the claim doesn't qualify, period, and interest instead starts at the date of judgment under the general statute.
Simple or compound
Neither the general judgment-interest statute nor the legal-rate statute mentions compounding. Both describe a continuing annual rate applied to a principal sum, and Washington practice treats this as simple interest rather than compounding.
Claims against the government
Washington doesn't bar prejudgment or post-judgment interest against a public agency the way some states do. Instead, it sets a different rate: a tort judgment against a "public agency" (state agencies, counties, cities, school districts, and similar political subdivisions) draws interest at 2 points above the 26-week Treasury bill yield, rather than the 2-points-above-prime rate that applies to a private tort defendant. That's a rate adjustment, not an exclusion, a liquidated claim against a government entity can still earn true prejudgment interest under the same common-law rule that applies to anyone else.
Other exceptions
Because the tort and catch-all rates are tied to published financial benchmarks reset every month, the exact rate can depend on the judgment-entry month. Medical debt is capped separately at 9% prejudgment interest. When a liquidated claim is offset by an opposing unliquidated counterclaim, Washington generally calculates prejudgment interest on the liquidated amount before the offsetting deduction. ESSB 5993 would have reduced interest on new or unpaid medical debt to 1%, but it returned to Senate Rules on March 12, 2026, without final passage, and the regular session adjourned sine die that day.
What trips people up
The biggest misconception is assuming Washington sorts prejudgment interest by contract versus tort the way many states do. It doesn't, the liquidated/unliquidated line cuts across both categories, so a tort claim with an exactly computable dollar amount (repair costs, an unpaid invoice recharacterized as negligence, etc.) can get true prejudgment interest, while a contract claim requiring expert testimony to value the damages might not.
People also tend to assume a tort judgment automatically earns interest from the date of the injury, the way it does in some other states. Under Washington's general judgment-interest statute, it doesn't, interest on an ordinary (unliquidated) tort judgment starts only when the judgment is entered, and a 2021-2022 effort to change that specifically for tort claims died in the legislature.
The offset rule for competing claims is a frequent surprise in commercial disputes: a party with a liquidated claim that gets partly offset by the other side's unliquidated counterclaim still gets prejudgment interest calculated on the FULL liquidated amount, not the smaller net figure left after the offset.
Common questions
Do I get prejudgment interest if I win a personal injury case in Washington? Not usually, unless your damages are liquidated (exactly computable without judicial discretion), most personal injury verdicts involve pain and suffering or other damages that require a jury's judgment to value, so they don't qualify. The judgment instead draws interest from the date it's entered.
What's Washington's prejudgment interest rate? For a liquidated claim, ordinarily 12% per year unless the parties agreed to a different rate in writing; medical-debt prejudgment interest is capped at 9%. Once judgment is entered, the applicable rate depends on the judgment type, the contract's own rate, a Treasury-bill-based rate for a government tort defendant, or prime plus 2 points for other tort defendants.
Can I get prejudgment interest on an unpaid invoice or contract debt? Yes, if the amount is fixed and ascertainable, Washington's liquidated-damages doctrine lets you recover interest from the date the debt became due, not just from the date of judgment.
Does the government get a break on interest in Washington? Not an exemption, but a different (usually lower) rate: a tort judgment against a public agency uses a Treasury-bill-based formula instead of the prime-rate formula that applies to private defendants.
Statutes and sources
- RCW 4.56.110(1), (3), (6) (interest on judgments) — quoted in the source record above. Accessed 2026-08-24: https://app.leg.wa.gov/rcw/default.aspx?cite=4.56.110
- RCW 19.52.010(1)-(2) (legal rate and medical-debt cap) — quoted in the source record above. Accessed 2026-08-24: https://app.leg.wa.gov/rcw/default.aspx?cite=19.52.010
- Mall Tool Co. v. Far West Equipment Co., 45 Wn.2d 158, 169 (1954). Accessed 2026-08-24: https://www.courtlistener.com/opinion/1151388/mall-tool-co-v-far-west-equipment-co/
The authorities are in general agreement that, when an amount claimed is "liquidated" or when the amount of an "unliquidated" claim is ascertainable by computation, interest is allowed as damages for the withholding of the amount due.
- Prier v. Refrigeration Engineering Co., 74 Wn.2d 25, 32 (1968). Accessed 2026-08-24: https://www.courtlistener.com/opinion/1161393/prier-v-refrigeration-engineering-co/
The rule in Washington is that interest prior to judgment is allowable (1) when an amount claimed is "liquidated" or (2) when the amount of an "unliquidated" claim is for an amount due upon a specific contract for the payment of money and the amount due is determinable by computation with reference to a fixed standard contained in the contract, without reliance on opinion or discretion.
Source links
Every statute quoted above, linked, with the date we checked it.
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