Montana: Prejudgment Interest Rules

The short answer

Montana runs three separate tracks for prejudgment interest, and which one applies depends on the kind of claim. A contract or debt-type claim for a sum that's certain or calculable draws interest as a matter of right under Mont. Code Ann. § 27-1-211, at the general 10% legal rate, running from the day the right to recover vested. A tort claim -- an "injury" to a person or to property -- goes through a separate, more specific statute instead, § 27-1-210: a floating rate (the Federal Reserve's prime rate plus 3%) that only starts running 30 days after the claimant sends the defendant a written statement itemizing the claim, and that never reaches damages like pain and suffering, mental anguish, or punitive damages, because those aren't "capable of being made certain by calculation." On top of both, a third and narrower provision, § 27-1-212, lets a jury add discretionary interest for a non-contract obligation or any case involving oppression, fraud, or malice -- except that this discretionary layer is expressly turned off in a claim against a governmental entity.

Requirements one by one

Governing law

Three statutes, each doing different work. § 27-1-211, "Right to interest," is the oldest and most general: it grants a mandatory right to interest whenever a claimant's damages are "certain or capable of being made certain by calculation" and the right to recover vested on a particular day -- the kind of claim that typically means a debt, an account, or another contract-type obligation. § 27-1-210, "Interest on torts," is a later, narrower statute that takes over for any claim on an "injury" as defined in § 27-1-106 (which covers both personal-injury and property-damage torts), replacing § 27-1-211's mechanism with its own rate and its own accrual trigger. § 27-1-212, "When award of interest discretionary," adds a further, separate layer available only for a non-contractual obligation or a case of oppression, fraud, or malice, left entirely to the jury's discretion.

Interest rate

Each track has its own rate. Under § 27-1-211, the statute itself doesn't state a number -- Montana courts have long read it together with the state's general legal-interest statute, § 31-1-106, which sets a default rate of 10% a year (described in Montana case law as a "10% simple interest rate"), unless a written contract fixes a different rate. Under § 27-1-210, the rate floats: the prime rate published in the Federal Reserve's H.15 statistical release, plus 3 percentage points, reset every January 1 and held through December 31. Under § 27-1-212, there's no statutory rate at all -- the jury decides the interest amount itself, at its own discretion.

When interest starts running

Under § 27-1-211, interest starts on "that particular day" the right to recover the certain or calculable sum vested -- typically the date a debt became due -- except that no interest accrues during any period the debtor was legally prevented, or prevented by the creditor's own conduct, from paying. Under § 27-1-210, the trigger is different and more procedural: interest starts 30 days after the claimant presented the opposing party (or their agent) a written statement setting out the claim and showing how the specific dollar amount was calculated -- not the date of injury, and not the date suit was filed.

Contract vs. tort claims

This is Montana's central axis, genuinely split by claim type but with a third layer added on top. A contract or debt-type claim (a vested right to a certain or calculable sum) runs through § 27-1-211's general mechanism. A tort claim -- an "injury" to person or property -- is carved out entirely into § 27-1-210, which imposes its own floating rate, its own written-presentment trigger, and a list of damages categories the mechanism simply doesn't reach (pain and suffering, mental anguish, injury to credit or reputation, punitive damages, loss of consortium or established way of life, and attorney fees, none of which are "capable of being made certain by calculation"). Layered on top of both, § 27-1-212 gives a jury a further, discretionary interest option specifically for a non-contractual obligation or any case of oppression, fraud, or malice -- a category that can overlap with tort claims already covered by § 27-1-210, but decided by the jury rather than treated as an entitlement.

Mandatory or discretionary

§ 27-1-211 and § 27-1-210 are both framed as entitlements -- "is entitled to interest" -- not something a court can simply decline once the statutory conditions are satisfied. That said, § 27-1-210(3) specifically directs that the jury be told the court, not the jury, will calculate the actual prejudgment interest due. § 27-1-212 stands apart as Montana's one genuinely discretionary interest provision: for a non-contract obligation or a case of oppression, fraud, or malice, interest "may be given, in the discretion of the jury" -- a jury call, not a formula.

Simple or compound

Simple interest throughout. Montana courts describe § 31-1-106's 10% rate -- the rate that underlies a § 27-1-211 award -- as a "10% simple interest rate." A related statute governing interest on judgments generally, § 25-9-205(1), states directly that "the interest may not be compounded."

Claims against the government

No Montana statute bars prejudgment interest against the State or a political subdivision outright, and the general tort damages cap that applies to government defendants -- $750,000 per claim and $1.5 million per occurrence under § 2-9-108 -- doesn't say one way or the other whether prejudgment interest counts inside or outside that dollar limit; this survey didn't locate a case resolving the question either way. Two real, located limits do apply to government defendants specifically. First, § 27-1-212's discretionary jury-awarded interest for a non-contract obligation or a case of oppression, fraud, or malice expressly "does not apply" to a claim for injury to a person or property brought against a governmental entity under the Montana Tort Claims Act (Title 2, chapter 9, parts 1-3). Second, § 2-9-317 gives a governmental entity a 2-year grace period after judgment is entered to pay the judgment without owing "any penalty or interest" -- a rule that, by its own terms, addresses interest running after judgment, not the prejudgment interest already folded into the judgment amount by the time it's entered.

Other exceptions

§ 27-1-210(2)'s exclusion list is the sharpest limit in the whole scheme: it bars interest entirely on damages "not capable of being made certain by calculation," expressly naming pain and suffering, injury to credit/reputation/financial standing, mental anguish or suffering, exemplary or punitive damages, loss of established way of life, loss of consortium, and attorney fees, plus any future damages until they're actually incurred. § 27-1-211 has a narrower built-in pause of its own: interest simply doesn't run for any period the debtor was prevented by law, or by the creditor's own act, from paying the debt.

What trips people up

The most common mistake is assuming one statute covers all of Montana's prejudgment interest. It takes three, and mixing them up matters: applying § 27-1-211's vested-right accrual date to a tort claim, instead of § 27-1-210's 30-days-after-written-presentment trigger, can move the start date by months. Forgetting to send that written, itemized statement of the claim at all is worse -- without it, a tort claimant's interest clock under § 27-1-210 never starts.

The second trap is assuming any calculable tort damages draw interest. § 27-1-210's list of excluded categories is long and covers most of what actually makes a personal-injury verdict large -- pain and suffering, mental anguish, punitive damages -- leaving interest to apply mainly to the more mechanical economic-damages figures like medical bills and lost wages.

Common questions

What's Montana's prejudgment interest rate?
It depends on the claim. A contract or debt claim draws 10% under § 27-1-211/§ 31-1-106. A tort claim draws a floating prime-plus-3% rate under § 27-1-210, reset every January 1.

Do I need to do anything before my tort claim starts drawing interest in Montana?
Yes -- send the opposing party a written statement of your claim showing how you calculated the specific dollar amount. Interest under § 27-1-210 doesn't start until 30 days after that statement is presented.

Can I get prejudgment interest on my pain-and-suffering damages in Montana?
No. § 27-1-210(2) expressly excludes pain and suffering, along with several other non-economic and punitive damages categories, because they can't be "made certain by calculation."

Can I get prejudgment interest if I sue the State of Montana or a county?
Possibly, but Montana's jury-discretionary interest under § 27-1-212 is expressly turned off against a governmental entity, and this survey found no case addressing whether ordinary prejudgment interest sits inside or outside the government's $750,000/$1.5 million tort damages cap.

Statutes and sources

• Mont. Code Ann. § 27-1-211 -- "Each person who is entitled to recover damages certain or capable of being made certain by calculation and the right to recover that is vested in the person upon a particular day is entitled also to recover interest on the damages from that day except during the time that the debtor is prevented by law or by the act of the creditor from paying the debt." Accessed 2026-07-05: https://law.justia.com/codes/montana/title-27/chapter-1/part-2/section-27-1-211/
• Mont. Code Ann. § 27-1-210 -- "in an action for recovery on an injury as defined in 27-1-106, a prevailing claimant is entitled to interest at a rate equal to the prime rate published by the federal reserve system in its statistical release H.15 Selected Interest Rates... plus 3%, on any claim for damages awarded that are capable of being made certain by calculation, beginning from the date 30 days after the claimant presented a written statement to the opposing party... The interest provisions... do not apply to damages not capable of being made certain by calculation, including... pain and suffering; injury to credit, reputation, or financial standing; mental anguish or suffering; exemplary or punitive damages; loss of established way of life; loss of consortium; and attorney fees." Accessed 2026-07-05: https://mca.legmt.gov/bills/mca/title_0270/chapter_0010/part_0020/section_0100/0270-0010-0020-0100.html
• Mont. Code Ann. § 27-1-212 -- "In an action for the breach of an obligation not arising from contract and in every case of oppression, fraud, or malice, interest may be given, in the discretion of the jury. This section does not apply in actions for recovery of damages arising from injury to a person or property brought against a governmental entity under Title 2, chapter 9, parts 1 through 3, as amended." Accessed 2026-07-05: https://mca.legmt.gov/bills/2007/mca/27/1/27-1-212.htm
• Mont. Code Ann. § 31-1-106(1) -- "...interest is payable on all money at the rate of 10% a year after it becomes due on: (a) any instrument of writing, except a judgment; (b) an account stated; (c) money lent or due on any settlement of accounts from the date on which the balance is ascertained; and (d) money received for the use of another person and detained from that person." Accessed 2026-07-05: https://mca.legmt.gov/bills/2007/mca/31/1/31-1-106.htm
• Mont. Code Ann. § 2-9-317 -- "Except as provided in 18-1-404(1)(b), if a governmental entity pays a judgment within 2 years after the day on which the judgment is entered, no penalty or interest may be assessed against the governmental entity." Accessed 2026-07-05: https://mca.legmt.gov/bills/2007/mca/2/9/2-9-317.htm