Oregon: Prejudgment Interest Rules

The short answer

Oregon doesn't split prejudgment interest by contract versus tort. One statute, ORS
82.010(1)(a), sets a 9%-a-year rate on "all moneys after they become due," and Oregon
courts have spent decades glossing that single sentence into the rule that actually
controls: interest is available whenever damages are "ascertainable" -- either a fixed
amount or one that can be calculated from a known formula or standard, as of an
identifiable date -- regardless of what label the claim carries. A fixed contract debt
almost always qualifies. A personal-injury claim for pain and suffering almost never
does, not because it's a tort but because there's no formula to compute it before a
jury sets the number. A property-damage or business-tort claim with a known repair
cost or contractual valuation formula can qualify exactly like a contract claim. Once
ascertainability is shown, interest follows automatically, as a matter of law -- it
isn't left to the court's sense of fairness. Oregon's state government and its
counties, however, are immune from paying prejudgment interest at all unless the
legislature has expressly said so; that immunity doesn't extend to cities.

Requirements one by one

Governing law

ORS 82.010(1)(a) is the entire statutory basis: it sets a 9% rate "payable on ...
[a]ll moneys after they become due." Oregon has never enacted a separate
prejudgment-interest statute for tort claims, or a separate one for contract claims --
everything runs through this one general interest provision. What actually decides
whether a given claim gets prejudgment interest is not the statute's text (which
doesn't mention "prejudgment interest" at all) but a long line of Oregon Court of
Appeals and Supreme Court decisions construing it, starting with Krieg v. Union Pac.
Land Resources Corp. (1974) and continuing through Strader v. Grange Mutual Ins. Co.
(2002), Miller v. C.C. Meisel Co. (2002), and Spaid v. 4-R Equipment (2012).

Interest rate

9% a year by default under ORS 82.010(1) -- but that default only applies "if the
parties have not otherwise agreed to a rate of interest." If there's a written
contract that sets its own rate, that rate controls instead, even if it's far above
9%; courts do still police an extreme contract rate as an unenforceable penalty in
egregious cases.

When interest starts running

For a contract debt, from the date the money became due. For a claim where the
amount wasn't fixed by agreement -- most tort claims, and any contract claim without
a stated price -- from the date the damages became ascertainable: a sum certain, or a
figure calculable from a known formula or standard. Oregon courts have been explicit
that this can be an earlier date than the date of judgment, or even earlier than the
date a jury resolves disputed facts, because "even though damages are not
ascertainable until issues of fact have been decided [by the jury], prejudgment
interest is proper" -- the jury's later fact-finding can retroactively confirm an
amount that was always calculable from an earlier, fixed date.

Contract vs. tort claims

Oregon draws no formal line between contract and tort claims for this purpose --
both run through the same statute and the same two-part ascertainability test: (1)
is the exact amount of damages ascertained or readily ascertainable, and (2) is the
date interest should start easily ascertained? In practice, that produces a pattern
that looks similar to a contract/tort split without actually being one: a fixed
contract debt almost always clears the test, while a personal-injury claim for pain
and suffering almost never does, because there's no formula to price it before
verdict. But a tort claim for property damage with a known repair cost, or a business
tort with a contractually defined damages formula, clears the same test a contract
claim would.

Mandatory or discretionary

Mandatory as a matter of law once ascertainability is established -- Oregon courts
describe the determination of the accrual date and the calculability of the amount as
questions decided "as a matter of law," not questions of equitable discretion for the
judge to weigh. The one place discretion-like uncertainty enters is procedural: if the
facts needed to fix the date or the amount are genuinely disputed between the parties,
that threshold factual question belongs to the jury, and a court can't award
prejudgment interest without a jury finding (or an undisputed record) resolving it
first.

Simple or compound

ORS 82.010 never says, one way or the other, whether the prejudgment rate under
subsection (1)(a) compounds -- only the separate POSTjudgment provision, subsection
(2)(b), expressly calls that different phase's interest "simple interest, unless
otherwise provided by contract." Consistent with that pattern, a federal court
applying Oregon law has treated the default 9% prejudgment rate as simple interest
when no contract specified otherwise. A written contract's own rate can itself
provide for compounding, and that term will control instead of the statutory default
-- though courts will still strike an extreme compounding rate as an unenforceable
penalty.

Claims against the government

Oregon's state government, and counties as instrumentalities of the state, are immune
from paying prejudgment interest entirely unless the legislature has expressly
authorized it -- "only clear expression by the legislature waives the state's
sovereign immunity." The Oregon Supreme Court has squarely held that ORS 82.010(1)(a)
itself, the general interest statute everyone else relies on, is NOT that
authorization: a claimant who relied on it to seek prejudgment interest against the
state lost, because the legislature never expressly said the general interest statute
applies to the state. That immunity, notably, does not extend to cities, which are
treated as ordinary parties for interest purposes.

Other exceptions

A written contract's own interest rate and compounding terms displace the statutory
9% default entirely, for better or worse -- courts will enforce a higher contract
rate but will void an extreme one as a penalty. Separately, ORS 82.010(2)(f) sets a
special, lower interest rate (the lesser of 5% a year or 3% over the Federal Reserve
discount rate) for judgments in medical-malpractice cases -- but that's a
POSTjudgment rate only, inside the different subsection (2) that governs interest
after judgment is entered. It has nothing to do with prejudgment interest and is an
easy trap for anyone skimming the statute.

What trips people up

Assuming ORS 82.010 is a contract-only statute, because it never uses the words
"tort" or "prejudgment," is the single biggest misreading. The statute is claim-type
neutral; the ascertainability test built on top of it by case law is what actually
sorts claims, and it sorts by whether the damages have a knowable number and date --
not by the label on the complaint.

Confusing the special medical-malpractice rate in ORS 82.010(2)(f) with a general
prejudgment rate is a second trap: that lower rate is postjudgment-only, and it
applies regardless of whether the defendant is the medical professional personally or
another party found liable for the professional negligence.

Assuming the state waived its interest immunity just by allowing itself to be sued at
all is a third trap. Oregon's courts have rejected that inference repeatedly:
submitting to liability for the underlying claim is not the same as consenting to pay
interest on it, and the general interest statute doesn't supply that consent by
itself.

Common questions

What's Oregon's prejudgment interest rate?
9% a year under ORS 82.010(1), unless a written contract sets a different rate.

Can I get prejudgment interest on an Oregon personal injury claim?
Only if the damages are ascertainable -- a fixed or formula-calculable amount as of an
identifiable date. Ordinary pain-and-suffering damages usually aren't, because a jury
sets that figure without a fixed formula; a property-damage claim with a known repair
cost is more likely to qualify.

Does Oregon prejudgment interest compound?
Not by default -- the statutory 9% rate is treated as simple interest. A written
contract can specify compounding instead, and that term will control if the contract
applies.

Can I get prejudgment interest against the State of Oregon or an Oregon county?
Generally no. The state and its counties are immune from prejudgment interest unless
the legislature has expressly authorized it for that specific claim; the general
interest statute alone does not count as that authorization. Cities don't share this
immunity.

Statutes and sources

• ORS 82.010(1)(a) -- "The rate of interest for the following transactions, if the
  parties have not otherwise agreed to a rate of interest, is nine percent per annum
  and is payable on: (a) All moneys after they become due." Accessed 2026-07-05:
  https://www.oregonlegislature.gov/bills_laws/ors/ors082.html
• ORS 82.010(2)(f) -- sets the lesser 5%-or-prime-plus-3% POSTjudgment rate for
  medical-malpractice judgments. Accessed 2026-07-05:
  https://www.oregonlegislature.gov/bills_laws/ors/ors082.html
• Strader v. Grange Mutual Ins. Co., 179 Or. App. 329, 338 (2002) -- "a trial court
  may award prejudgment interest on damages only when the exact amount is ascertained
  or easily ascertainable." Accessed 2026-07-05:
  https://law.justia.com/cases/oregon/court-of-appeals/2002/a110669.html
• Spaid v. 4-R Equipment, LLC, 252 Or. App. 46 (2012) -- collects and applies the
  ascertainability test from Krieg v. Union Pac. Land Resources Corp. (1974) and
  Goodyear Tire & Rubber Co. v. Tualatin Tire & Auto (1994). Accessed 2026-07-05:
  https://caselaw.findlaw.com/court/or-court-of-appeals/1611777.html
• Newport Church of the Nazarene v. Hensley, 335 Or. 1, 17 (2002) -- holds the
  state is immune from prejudgment interest absent express legislative authorization.
  Accessed 2026-07-05: https://www.courtlistener.com/opinion/835997/
• Young v. State of Oregon, 346 Or. 507, 515 (2009) -- reaffirms that ORS
  82.010(1)(a) itself is not that authorization. Accessed 2026-07-05:
  https://www.courtlistener.com/opinion/835163/
• Avenue 33, LLC v. Aventurine Capital Group, LLC, No. 3:23-cv-00896-YY (D. Or.
  Apr. 10, 2024) -- applies the default 9% statutory rate as simple interest.
  Accessed 2026-07-05:
  https://www.govinfo.gov/content/pkg/USCOURTS-ord-3_23-cv-00896/pdf/USCOURTS-ord-3_23-cv-00896-1.pdf