Wyoming: Prejudgment Interest Rules
The short answer
Yes, through case law built on top of a general interest-rate statute rather than a dedicated prejudgment-interest statute. Wyoming courts award prejudgment interest whenever a two-part test is met: the claim must be liquidated (readily computable by simple math) and the debtor must have received notice of the amount due before interest starts running. This test applies the same way regardless of whether the underlying claim is contract or tort. The rate is 7% a year, borrowed from the state's general 'legal rate of interest' statute, unless the parties' contract sets a different rate. A mere dispute over liability, or even an unliquidated counterclaim, doesn't defeat an otherwise-liquidated claim's right to interest. Claims against a Wyoming state or local government entity are different: prejudgment interest is barred outright by statute.
| Governing law | Wyoming has no dedicated prejudgment-interest statute. The right comes from a long line of Wyoming Supreme Court cases -- most recently and comprehensively restated in Ropken v. YJ Construction, Inc., 2025 WY 131 (Dec. 2025) -- built on top of two general-purpose statutes: Wyo. Stat. Ann. § 40-14-106(e), part of the Wyoming Uniform Consumer Credit Code, which Wyoming courts have borrowed as the default prejudgment-interest rate; and W.S. § 1-16-102(a), a separate statute governing interest on judgments after they're entered (a different, higher rate, addressed below) |
|---|---|
| Interest rate | 7% a year, drawn from Wyo. Stat. Ann. § 40-14-106(e) -- 'If there is no agreement or provision of law for a different rate, the interest of money shall be at the rate of seven percent (7%) per annum' -- which the Wyoming Supreme Court has confirmed is the default prejudgment-interest rate absent a contractual rate. This is a genuinely different figure from the postjudgment rate: W.S. § 1-16-102(a) sets interest on the judgment itself, once entered, at 10% a year. A written contract's own agreed rate controls over either default if the parties specified one |
| When interest starts running | From the date the debtor received notice of the amount due -- typically a formal demand or demand letter specifying a sum certain -- not from the date of breach, injury, or the eventual court judgment. Calculating interest only from the date of a jury's damages finding, rather than from the earlier notice date, would improperly convert prejudgment interest into something closer to postjudgment interest, defeating its purpose of compensating for the whole period the money was wrongfully withheld |
| Contract vs. tort claims | Wyoming's test doesn't split by claim type -- it turns entirely on whether the specific damages claimed are liquidated (readily computable by simple math) versus unliquidated. This has most often been applied to breach-of-contract claims with invoices or a sum-certain demand, but the underlying case law traces back to a broader liquidated-versus-unliquidated distinction that in principle reaches any claim type, including a tort claim, wherever the damages are similarly sum-certain and preceded by adequate notice. A claim doesn't become unliquidated merely because the defendant disputes liability or the exact amount owed, or because the defendant asserts an unliquidated counterclaim or set-off against it |
| Mandatory or discretionary | Once the two-part test (liquidated claim, notice given) is satisfied, Wyoming's courts have described the right to interest as following 'as a matter of law,' not as a jury question or a matter of grace -- older cases put it as directly as saying a prevailing party 'should not be mulcted of a part of his rightful judgment' by being denied interest. Procedurally, though, appellate review has two layers: whether a district court is legally entitled to consider awarding prejudgment interest is reviewed de novo, while whether prejudgment interest should actually be awarded on the facts of a given case is reviewed for abuse of discretion. Wyoming's courts have also confirmed a district court may decide the prejudgment-interest question after a jury has already decided liability and damages -- it isn't a question reserved for the jury |
| Simple or compound | This survey did not locate a Wyoming statute or case squarely addressing whether prejudgment interest compounds; the cases reviewed describe the calculation only in terms of 'simple mathematic calculations' applied to a stated rate over a stated number of days, consistent with simple interest, but none states this as an express holding on compounding one way or the other |
| Claims against the government | Prejudgment interest against a Wyoming governmental entity is barred outright, not merely capped. The Wyoming Governmental Claims Act states plainly: 'No judgment against a governmental entity shall include an award for exemplary or punitive damages, for interest prior to judgments or for attorney's fees.' Separately, total liability under the Act -- for the state, a county, city, or other local government, and any public employee acting within the scope of duty -- is capped at $250,000 to any one claimant and $500,000 for all claims arising from a single occurrence, regardless of the prejudgment-interest bar |
| Other exceptions | A claim that starts out unliquidated can still become liquidated -- and therefore eligible for prejudgment interest -- if the amount can eventually be determined without reliance on opinion or discretion, for instance once it's fixed by a formula or a specific, itemized demand. Conversely, Wyoming's courts have declined prejudgment interest where the verdict doesn't allow the reviewing court to separate out which portion of a jury's award corresponded to a liquidated component (like specific medical bills) versus an unliquidated one, since interest can't be calculated on an amount that can't be isolated. A claim for attorney's fees has also been held not to qualify as a liquidated claim for these purposes |
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The short answer
Wyoming doesn't have a dedicated prejudgment-interest statute -- the right comes from decades of Wyoming Supreme Court case law, most recently restated in a December 2025 decision. Interest is available whenever two conditions are met: the claim has to be liquidated, meaning the amount is readily computable by simple math, and the party owing the money has to have received notice of the amount due before interest starts running. This test doesn't split by claim type -- it applies the same way whether the underlying dispute is a breach of contract or something else, so long as the specific damages at issue are sum-certain and preceded by adequate notice. The rate is 7% a year, borrowed from the state's general legal-interest-rate statute, unless the parties' own contract sets a different figure. Disputing liability, or even asserting an unliquidated counterclaim, doesn't turn an otherwise-liquidated claim into an unliquidated one. Claims against the State of Wyoming or a local government work differently: prejudgment interest is barred outright by statute, full stop.
Requirements one by one
Governing law
There's no comprehensive prejudgment-interest statute in Wyoming. The Wyoming Supreme Court has built the rule almost entirely through case law, most recently and thoroughly restated in Ropken v. YJ Construction, Inc., decided in December 2025. That case law leans on two separate general-purpose statutes for its mechanics: Wyo. Stat. Ann. § 40-14-106(e), a provision of the Wyoming Uniform Consumer Credit Code that sets a general "legal rate of interest," which Wyoming courts have adopted as the default prejudgment-interest rate even outside the consumer-credit context; and W.S. § 1-16-102(a), an entirely separate statute that sets the rate a judgment bears once it's actually entered -- a different figure, addressed below.
Interest rate
7% a year, under Wyo. Stat. Ann. § 40-14-106(e) -- "the interest of money shall be at the rate of seven percent (7%) per annum" absent an agreement or a different statutory rate -- which the Wyoming Supreme Court has confirmed applies as the default prejudgment-interest rate. This is a genuinely different number from Wyoming's postjudgment rate: once a judgment is entered, W.S. § 1-16-102(a) takes over and sets that rate at 10% a year instead. If the parties' own contract specifies its own interest rate, that rate governs over either statutory default.
When interest starts running
From the date the debtor received notice of the amount owed -- typically a demand letter or similar communication that specifies a sum certain -- not from the date of the underlying breach or injury, and not from the date a jury eventually returns a damages verdict. Calculating interest only from the date of the jury's verdict, rather than from the earlier notice date, would defeat the purpose of prejudgment interest by effectively converting it into postjudgment interest, since it's meant to compensate for the entire period the money was wrongfully withheld, not just the period after trial.
Contract vs. tort claims
Wyoming's test doesn't turn on whether the claim is contract or tort -- it turns on whether the specific damages sought are liquidated (readily computable by simple math) or unliquidated. In practice, most of the reported cases involve a breach-of-contract claim tied to invoices or a sum-certain demand, but the underlying liquidated/unliquidated distinction is not, by its own terms, limited to contract claims -- it reaches any claim type where the damages are similarly precise and preceded by adequate notice. A claim doesn't lose its liquidated character just because the defendant disputes liability altogether, disputes part of the amount, or raises an unliquidated counterclaim or set-off against it.
Mandatory or discretionary
Once the two-part test -- a liquidated claim, and notice given before interest starts -- is satisfied, Wyoming's courts have said the right to interest follows "as a matter of law," language echoing older cases holding that a prevailing party "should not be mulcted of a part of his rightful judgment" by having interest denied. That said, appellate review operates on two levels: whether a district court is legally entitled to even consider awarding prejudgment interest is a question of law reviewed de novo, while whether prejudgment interest should actually be awarded, given the specific facts, is reviewed only for abuse of discretion. Wyoming's courts have also confirmed that a district court can decide the prejudgment-interest question itself even after a jury has already returned a verdict on liability and damages -- it isn't treated as something reserved exclusively for the jury.
Simple or compound
This survey did not locate a Wyoming statute or case that squarely addresses compounding. The cases reviewed describe the calculation only in terms of "simple mathematic calculations" applied to a stated rate over a stated number of days -- consistent with simple interest -- but none of them states this as an express holding on the simple-versus-compound question.
Claims against the government
Prejudgment interest against a Wyoming governmental entity isn't just capped -- it's barred outright. The Wyoming Governmental Claims Act says plainly that "no judgment against a governmental entity shall include an award for exemplary or punitive damages, for interest prior to judgments or for attorney's fees." Separately, and regardless of the interest bar, the Act caps total liability -- for the State, a county, city, school district, or other local government entity, and any public employee acting within the scope of duty -- at $250,000 to any one claimant and $500,000 for all claims arising out of a single occurrence.
Other exceptions
A claim that starts out unliquidated can still become eligible for prejudgment interest if the amount can eventually be determined without reliance on opinion or discretion -- for instance, once a specific, itemized demand fixes the number precisely. Working the other direction, Wyoming's courts have declined to award prejudgment interest where a jury's verdict doesn't allow the reviewing court to isolate which portion of the award corresponded to a liquidated item (like specific medical expenses) as opposed to an unliquidated one, since interest can't meaningfully be calculated on an amount that can't be separated out. A claim for attorney's fees has also been held not to qualify as a liquidated claim capable of drawing prejudgment interest.
What trips people up
The most common mistake is assuming prejudgment interest starts running from the date of a breach or injury. In Wyoming, it starts from the date the other side received notice of the specific amount owed -- typically a demand letter -- which can be considerably later than the date the underlying loss occurred. Waiting too long to send a clear, itemized demand can cost real money in lost interest.
The second trap is assuming a genuine factual dispute defeats a claim's liquidated status. It doesn't -- Wyoming's courts have repeatedly held that disputing liability, disputing part of the amount, or raising an unliquidated counterclaim doesn't convert an otherwise sum-certain claim into an unliquidated one. What matters is whether the claimed amount itself was readily computable and clearly communicated, not whether the other side agreed they owed it.
Common questions
What's Wyoming's prejudgment interest rate?
7% a year, under Wyo. Stat. Ann. § 40-14-106(e), unless the parties' contract sets a different rate. This is different from the 10% rate that applies to a judgment after it's entered.
Do I get prejudgment interest automatically once I win my case in Wyoming?
Not automatically -- your damages have to be liquidated (readily computable by simple math), and the other side has to have received notice of the specific amount before interest starts running. A court still has to find both conditions are met.
Does a factual dispute over how much I'm owed prevent me from getting prejudgment interest in Wyoming?
No. Wyoming's courts have held that a mere difference of opinion over the amount due, or even an unliquidated counterclaim against your claim, doesn't make your claim unliquidated.
Can I get prejudgment interest if I sue the State of Wyoming or a local government?
No. The Wyoming Governmental Claims Act expressly bars any award of prejudgment interest against a governmental entity, on top of its separate $250,000/$500,000 damages caps.
Statutes and sources
- Wyo. Stat. Ann. § 40-14-106(e) -- "If there is no agreement or provision of law for a different rate, the interest of money shall be at the rate of seven percent (7%) per annum." Accessed 2026-07-05: https://law.justia.com/codes/wyoming/title-40/chapter-14/article-1/section-40-14-106/
- W.S. § 1-16-102 -- "(a) Except as provided in subsections (b) and (c) of this section, all decrees and judgments for the payment of money shall bear interest at ten percent (10%) per year from the date of rendition until paid. (b) If the decree or judgment is founded on a contract and all parties to the contract agreed to interest at a certain rate, the rate of interest on the decree or judgment shall correspond to the terms of the contract." Accessed 2026-07-05: https://law.justia.com/codes/wyoming/title-1/chapter-16/article-1/section-1-16-102/
- W.S. § 1-39-118(a), (d) -- "(a) ... the liability of the governmental entity ... shall not exceed: (i) The sum of two hundred fifty thousand dollars ($250,000.00) to any claimant for any number of claims arising out of a single transaction or occurrence; or (ii) The sum of five hundred thousand dollars ($500,000.00) for all claims of all claimants arising out of a single transaction or occurrence. ... (d) No judgment against a governmental entity shall include an award for exemplary or punitive damages, for interest prior to judgments or for attorney's fees." Accessed 2026-07-05: https://law.justia.com/codes/wyoming/title-1/chapter-39/section-1-39-118/
Source links
Every statute quoted above, linked, with the date we checked it.