New Mexico: Prejudgment Interest Rules

The short answer

New Mexico splits prejudgment interest across two statutes that work very differently. If you're owed a debt whose amount could be pinned down by a fixed formula or market price, interest is yours as a matter of right, at up to 15% a year, running from when the money became due. For everything else — most tort claims, and any contract dispute that doesn't meet that ascertainable-amount standard — a court decides whether to award interest at all, capped at 10% a year and running only from the date the complaint was served, after weighing who caused delay in the case and whether either side made a reasonable settlement offer that got turned down.

Requirements one by one

Governing law

Two sections of the same statutory article do the work. Section 56-8-3 sets an as-of-right interest rate for money due on a contract, on money wrongfully retained, or on a matured, ascertained account balance. Section 56-8-4(B) is a separate, general prejudgment-interest mechanism that a court may apply to any civil judgment — not limited to torts — but is the only real option for tort claims, since those damages don't fit § 56-8-3's contract/ascertained-balance categories. A third statute, the Tort Claims Act's § 41-4-19, displaces both when the defendant is a government entity.

Interest rate

Under § 56-8-3, the rate is up to 15% a year, or whatever rate the parties' own written contract sets if it fixes a different one. Under § 56-8-4(B), a court's discretionary prejudgment interest award is capped lower, at 10% a year. (Section 56-8-4(A) separately sets the ordinary post-judgment rate at 8.75% a year, rising to 15% if the judgment rests on tortious conduct, bad faith, or intentional or willful acts — that elevated 15% figure is a post-judgment rate, not the prejudgment cap, and it's easy to confuse the two.)

When interest starts running

For a contract-type claim under § 56-8-3, interest runs from when the amount became due or the account balance was ascertained — which can be well before a lawsuit is ever filed. For the general discretionary mechanism under § 56-8-4(B), the statute sets a specific starting point: "from the date the complaint is served upon the defendant," not the date of injury or breach.

Contract vs. tort claims

A contract debt that's ascertainable by a fixed standard — a stated price, an established market value — gets interest as a matter of right under § 56-8-3. A tort claim (or a contract claim that doesn't meet that ascertainable-amount test) instead falls to § 56-8-4(B)'s discretionary mechanism, which applies the same way regardless of claim type but is genuinely optional rather than automatic. Post-judgment interest also splits by claim type: an ordinary judgment draws 8.75%, but a judgment resting on tortious conduct — which New Mexico courts have confirmed includes ordinary negligence, not just intentional wrongdoing — draws 15% after judgment.

Mandatory or discretionary

Section 56-8-3 interest is available as of right once the ascertainability threshold is met. Section 56-8-4(B) interest is squarely discretionary: New Mexico's Supreme Court has held the decision whether to award it at all belongs to the trial court, reviewed only for abuse of discretion, and a court doesn't even have to make specific findings when it denies the request — its reasoning only needs to be "ascertainable from the record and not contrary to logic and reason." Courts have upheld denying prejudgment interest even where the defendant's own pretrial settlement offer was far below the eventual award, if the case was genuinely complex enough to explain the delay.

Simple or compound

Simple interest under both statutes. No New Mexico authority located this session provides for compounding of ordinary civil prejudgment interest.

Claims against the government

The Tort Claims Act bars prejudgment interest outright against a governmental entity or a public employee sued for a waived-immunity tort — no exceptions for the underlying conduct's severity. Post-judgment interest still applies, but at its own floating rate: 2 percentage points above the prime rate published in the Wall Street Journal on the date judgment is entered, computed daily. This sits on top of the Tort Claims Act's separate damages caps (currently $200,000 for real-property damage, $300,000 for medical expenses, and $400,000 per person for other damages arising from a single occurrence, subject to a $750,000 aggregate ceiling). One narrow wrinkle: a state-created fund that pays claims on the state's behalf — for example, the medical-malpractice Patient's Compensation Fund — isn't automatically treated as "the state" for this exemption, and New Mexico's Court of Appeals has held such a fund can still owe its share of prejudgment and post-judgment interest.

Other exceptions

Section 56-8-4(B)'s discretionary mechanism doesn't apply to a judgment based on unpaid child support. Punitive and exemplary damages are barred against government tort defendants entirely, alongside the prejudgment-interest bar.

What trips people up

The two statutes' rate caps are easy to mix up: 15% is real, but it's the ceiling for an as-of-right contract claim under § 56-8-3, or the elevated post-judgment rate for a tortious judgment under § 56-8-4(A) — the actual discretionary prejudgment cap for a tort claim under § 56-8-4(B) is only 10%. Confusing "prejudgment" and "post-judgment" figures in this statute is a common, understandable mistake because both live in the same section.

People also sometimes assume a lowball settlement offer guarantees prejudgment interest once the plaintiff beats it at trial. It doesn't — New Mexico courts weigh the settlement-offer factor alongside others, including which side caused delay, and can still deny interest entirely if the case was genuinely difficult to resolve.

Common questions

What rate applies to an ordinary breach-of-contract claim in New Mexico?
Up to 15% a year under § 56-8-3 if the amount owed is ascertainable by a fixed standard; if it isn't, the claim instead goes through the discretionary § 56-8-4(B) mechanism, capped at 10%.

Can I get prejudgment interest on a personal-injury verdict in New Mexico?
Only if a court decides to award it under § 56-8-4(B) — it's discretionary, capped at 10%, and runs only from the date the complaint was served, not the date of injury.

Can I get prejudgment interest against the State of New Mexico?
No. The Tort Claims Act bars it outright for a claim against a governmental entity or employee, though post-judgment interest still applies at a floating rate.

Does interest compound in New Mexico?
No indication that it does under either statute; treat both as simple interest.

Statutes and sources

• NMSA 1978 § 56-8-3 — "The rate of interest, in the absence of a written contract fixing a different rate, shall be not more than fifteen percent annually in the following cases: A. on money due by contract; B. on money received to the use of another and retained without the owner's consent expressed or implied; and C. on money due upon the settlement of matured accounts from the day the balance is ascertained." Accessed 2026-07-05: https://law.justia.com/codes/new-mexico/chapter-56/article-8/section-56-8-3/
• NMSA 1978 § 56-8-4 — "A. Interest shall be allowed on judgments and decrees for the payment of money from entry and shall be calculated at the rate of eight and three-fourths percent per year, unless... (2) the judgment is based on tortious conduct, bad faith or intentional or willful acts, in which case interest shall be computed at the rate of fifteen percent. B. Unless the judgment is based on unpaid child support, the court in its discretion may allow interest of up to ten percent from the date the complaint is served upon the defendant after considering, among other things: (1) if the plaintiff was the cause of unreasonable delay in the adjudication of the plaintiff's claims; and (2) if the defendant had previously made a reasonable and timely offer of settlement to the plaintiff. ... D. The state and its political subdivisions are exempt from the provisions of this section except as otherwise provided by statute or common law." Accessed 2026-07-05: https://law.justia.com/codes/new-mexico/chapter-56/article-8/section-56-8-4/
• NMSA 1978 § 41-4-19(C)-(D) — "C. Interest shall be allowed on judgments against a governmental entity or public employee for a tort for which immunity has been waived under the Tort Claims Act at a rate equal to two percentage points above the prime rate as published in the Wall Street Journal on the date of the entry of the judgment... D. No judgment against a governmental entity or public employee for any tort for which immunity has been waived under the Tort Claims Act shall include an award for exemplary or punitive damages or for interest prior to judgment." Accessed 2026-07-05: https://law.justia.com/codes/new-mexico/chapter-41/article-4/section-41-4-19/
• Sunnyland Farms, Inc. v. Central New Mexico Electric Cooperative, Inc., 2013-NMSC-017 — "The decision whether or not to award prejudgment interest is within the discretion of the trial court, and we review only for abuse of that discretion... The court's reasons for denying prejudgment interest need only be ascertainable from the record and not contrary to logic and reason." Accessed 2026-07-05 via FindLaw case mirror, cross-checked via CourtListener (legalresearch tool).
• Massengill v. Fisher Sand & Gravel Co., No. 31,942 (N.M. Ct. App. Aug. 19, 2013) — confirms § 56-8-4(A) post-judgment interest is mandatory. Accessed 2026-07-05: https://coa.nmcourts.gov/wp-content/uploads/sites/43/2024/01/Massengill-FO.pdf
• Siebert v. Okun, No. A-1-CA-39966 (N.M. Ct. App. Sept. 23, 2024) — holds the medical-malpractice Patient's Compensation Fund is not "the state" for § 56-8-4(D)'s exemption and can owe its share of interest. Accessed 2026-07-05: https://coa.nmcourts.gov/wp-content/uploads/sites/43/2024/09/September-23-2024-Susan-L.-Siebert-v.-Rebecca-C.-Okun-M.D.-No.-A-1-CA-39966.pdf