Prejudgment Interest Rules in Wyoming

At a glance

Requirements one by one

Governing law

Wyoming's general rate provision says that, absent a different agreement or law, "the interest of money shall be at the rate of seven percent (7%) per annum" (§ 40-14-106(e)). The Wyoming Supreme Court supplies the prejudgment eligibility test in Ropken v. YJ Construction, Inc., 2025 WY 131, ¶ 10: the amount must be readily computable by simple mathematics, and the debtor must receive notice of the amount due.

Interest rate

The 7% default applies before judgment. Once a money judgment is entered, § 1-16-102(a) sets a separate 10% annual rate from the date of rendition; subsection (b) makes the agreed contract rate control for a judgment founded on a contract.

When interest starts running

Notice of the amount due starts the clock on an otherwise liquidated claim. In Ropken, the contractor sent a demand letter attaching three unpaid invoices, then the district court applied the 7% rate to the jury award from that notice date. A claim's breach or injury date alone does not establish the required notice.

Contract vs. tort claims

The court frames its test around the character of the damages and notice, rather than naming a contract-only rate. Its worked example in Ropken was an unpaid construction contract. For any claim, the particular damages must meet the same liquidated-amount inquiry; a verdict that does not identify the liquidated component can prevent calculation of interest (Ropken, ¶ 14).

Mandatory or discretionary

The court reviews whether a trial court may award prejudgment interest as a legal question, but reviews the factual award for abuse of discretion (Ropken, ¶ 7). The earlier Rissler & McMurry Co. v. Atlantic Richfield Co. decision described interest on a qualifying claim as following "as a matter of law." Both the computable amount and notice must be shown.

Claims against the government

Section 1-39-118(d) says a judgment against a governmental entity under the Governmental Claims Act cannot include "interest prior to judgments." The bar applies to an action under that act; it is separate from the ordinary private-party interest calculation.

What trips people up

A dispute over liability does not by itself make a sum-certain claim unliquidated (Ropken, ¶ 21). The harder issue is identifying the exact amount that qualifies. If a verdict combines liquidated and unliquidated damages without separating them, the court may be unable to calculate interest on the liquidated portion (Ropken, ¶ 14).

Common questions

Must I request prejudgment interest in the complaint? The Wyoming Supreme Court says omitting it from the complaint does not waive the request (Ropken, ¶ 16).

Can the judge decide interest after a jury verdict? Yes. A district court may consider and award prejudgment interest even when it was not the trier of fact (Ropken, ¶ 19).

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 2026-10-07: https://wyoleg.gov/statutes/compress/title40.pdf
• 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 2026-10-07: https://wyoleg.gov/statutes/compress/title01.pdf
• W.S. § 1-39-118(a), (d): “(a) Except as provided in subsection (b) of this section, in any action under this act, the liability of the governmental entity, including a public employee while acting within the scope of his duties, 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 2026-10-07: https://wyoleg.gov/statutes/compress/title01.pdf
• Ropken v. YJ Construction, Inc., 2025 WY 131, ¶ 10: “Prejudgment interest is available if a two-part test is met: (1) the claim must be liquidated, as opposed to unliquidated, meaning it is readily computable via simple mathematics; and (2) the debtor must receive notice of the amount due before interest begins to accumulate.” Accessed 2026-10-07: https://law.justia.com/cases/wyoming/supreme-court/2025/s-25-0001.html
• Ropken v. YJ Construction, Inc., 2025 WY 131, ¶ 19: “We further take this opportunity to expressly state that a district court has authority to and may consider and award prejudgment interest even when it is not the trier of fact.” Accessed 2026-10-07: https://law.justia.com/cases/wyoming/supreme-court/2025/s-25-0001.html
• Ropken v. YJ Construction, Inc., 2025 WY 131, ¶ 21: “A dispute as to liability does not make the claim unliquidated.” Accessed 2026-10-07: https://law.justia.com/cases/wyoming/supreme-court/2025/s-25-0001.html
• Ropken v. YJ Construction, Inc., 2025 WY 131, ¶ 16: “a party does not waive its request for prejudgment interest by omitting it from his complaint” Accessed 2026-10-07: https://law.justia.com/cases/wyoming/supreme-court/2025/s-25-0001.html
• Ropken v. YJ Construction, Inc., 2025 WY 131, ¶ 4: “On October 24, 2022, YJ provided the Ropkens with a demand letter, notifying them they still owed $276,169 for three unpaid invoices, which were attached to the demand letter.” Accessed 2026-10-07: https://law.justia.com/cases/wyoming/supreme-court/2025/s-25-0001.html
• Ropken v. YJ Construction, Inc., 2025 WY 131, ¶ 7: “Whether a district court is entitled to award prejudgment interest in a case is a question of law reviewed de novo; whether prejudgment interest should be awarded is reviewed for an abuse of discretion.” Accessed 2026-10-07: https://law.justia.com/cases/wyoming/supreme-court/2025/s-25-0001.html
• Ropken v. YJ Construction, Inc., 2025 WY 131, ¶ 14: “We found no error in the district court’s ruling because it was not possible to determine from the jury’s verdict what portion of the medical expenses were included in the award.” Accessed 2026-10-07: https://law.justia.com/cases/wyoming/supreme-court/2025/s-25-0001.html
• Rissler & McMurry Co. v. Atlantic Richfield Co., 559 P.2d 25, 34 (Wyo. 1977): “The right to interest followed as a matter of law and did not involve any question of fact. ... See also Engelberg v. Sebastiani, 1929, 207 Cal. 727, 279 P. 795, stating that there is no question of fact for a jury to decide, no function of the jury is usurped, interest is incident to an award of the contract price and the plaintiff should not be mulcted of a part of his rightful judgment.” Accessed 2026-10-07: https://www.courtlistener.com/opinion/1455862/