Prejudgment Interest Rules in Massachusetts

At a glance

Requirements one by one

Governing law

Two side-by-side statutes do the work: G.L. c. 231, § 6B covers tort actions ("personal injuries," "consequential damages," or "damage to property"), and § 6C covers "actions based on contractual obligations." A third section, § 6I, sets a separate, lower rate that applies only when the judgment runs against the commonwealth itself on a contract claim.

Interest rate

Both statutes set the same baseline rate: 12% a year. For a contract claim, that 12% is a fallback — if the parties' own contract fixed a rate, § 6C uses the contract's rate instead. For a contract judgment against the commonwealth, § 6C uses the contract rate if established; otherwise it redirects to § 6I’s weekly average one-year Treasury yield, capped at 10% a year. Tort claims have no equivalent government carve-out in the rate itself — the carve-out there is a complete bar, described below.

When interest starts running

For a tort claim under § 6B, interest always starts on "the date of commencement of the action" — when the lawsuit was filed, not when the injury happened. For a contract claim under § 6C, the clock can start earlier: on "the date of the breach or demand," if that date is established at trial. If no breach or demand date is proven, contract interest falls back to the same rule as tort claims, running from the date the action was filed.

Contract vs. tort claims

Massachusetts treats the two claim types almost identically — same 12% rate, same automatic clerk-added mechanics, same statutory design — but the accrual date is a real difference. A contract plaintiff who can prove an earlier breach or demand date gets more interest than a tort plaintiff automatically would, because tort interest is locked to the filing date no matter how much earlier the injury occurred.

Mandatory or discretionary

Neither statute gives a judge or jury any choice in the matter. Both say interest "shall be added by the clerk of court" — a ministerial, arithmetic step that happens automatically once a qualifying verdict, finding, or order for judgment is entered, not something either side has to request or a court has to approve.

Simple or compound

Neither § 6B nor § 6C expressly prescribes compounding. Both set an annual rate and direct the clerk to add interest to damages. A contractual rate provision may require separate analysis.

Claims against the government

This is where contract and tort diverge sharply. A contract judgment against the commonwealth still gets interest at the established contract rate, or otherwise at the floating § 6I rate capped at 10%. A tort judgment against a public employer is different in kind, not just in rate: the Massachusetts Tort Claims Act says public employers "shall not be liable for interest prior to judgment" at all — no prejudgment interest, period — on top of a separate $100,000 damages cap and an outright bar on punitive damages.

Other exceptions

The Tort Claims Act's interest bar travels together with its $100,000 compensatory-damages cap and its punitive-damages bar (with one carve-out: claims for serious bodily injury against the MBTA aren't subject to the $100,000 cap, though the interest bar itself still applies). Separately, S.1149 and H.1795 proposed replacing the twelve-percent default for private claims with a Treasury-yield formula. Their official histories show study-order dispositions in January and March 2026, with no enacted rate change.

What trips people up

The 12% rate is easy to confuse with market reality: it was fixed by the Legislature in 1982 and hasn't moved since, even though ordinary interest rates have been far lower for most of the time since. The Supreme Judicial Court addressed this directly in Greene v. Philip Morris USA Inc. (decided May 9, 2023), rejecting a due-process challenge to the fixed 12% rate and holding it survives rational-basis review because it's designed to make a plaintiff whole for the time value of money during a long case, not to punish the defendant.

The accrual-date difference between contract and tort claims matters more than it looks. A contract plaintiff who can prove an early breach or demand date can end up with years more interest than a tort plaintiff in an otherwise similar case, simply because tort interest is locked to the filing date no matter how much earlier the underlying injury occurred.

The government-defendant rules are not one rule — they're two different rules depending on claim type, and mixing them up is a common mistake. A contract claim against the state still earns interest, just at a lower, floating rate; a tort claim against a public employer earns no prejudgment interest at all. Don't assume "government defendant" means the same treatment across claim types.

Common questions

Is Massachusetts's 12% prejudgment interest rate really fixed, or does it change with market rates? It's fixed by statute at 12% a year for both contract and tort claims against private parties, and has stayed at 12% since 1982. S.1149 and H.1795 proposed a floating Treasury-yield formula and received study-order dispositions in 2026.

Does my personal injury case earn interest from the date I was hurt, or from when I filed suit? From when you filed suit. Tort interest under § 6B runs from "the date of commencement of the action," not the date of the underlying injury.

Can I get prejudgment interest if I sue a city or the Commonwealth of Massachusetts? It depends on the claim type. A contract claim against the commonwealth still earns interest at an established contract rate or the capped Treasury-yield rate under § 6I. A tort claim against a public employer earns no prejudgment interest at all under the Tort Claims Act.

Does the interest compound? Neither § 6B nor § 6C expressly directs compounding language.

Statutes and sources

• Mass. Gen. Laws ch. 231, § 6B — "In any action in which a verdict is rendered or a finding made or an order for judgment made for pecuniary damages for personal injuries to the plaintiff or for consequential damages, or for damage to property, there shall be added by the clerk of court to the amount of damages interest thereon at the rate of twelve per cent per annum from the date of commencement of the action even though such interest brings the amount of the verdict or finding beyond the maximum liability imposed by law." Accessed 2026-10-06: https://malegislature.gov/Laws/GeneralLaws/PartIII/TitleII/Chapter231/Section6B
• Mass. Gen. Laws ch. 231, § 6C — "In all actions based on contractual obligations, upon a verdict, finding or order for judgment for pecuniary damages, interest shall be added by the clerk of the court to the amount of damages, at the contract rate, if established, or at the rate of twelve per cent per annum from the date of the breach or demand. If the date of the breach or demand is not established, interest shall be added by the clerk of the court, at such contractual rate, or at the rate of twelve per cent per annum from the date of the commencement of the action, provided, however, that in all actions based on contractual obligations, upon a verdict, finding or order for judgment against the commonwealth for pecuniary damages, interest shall be added by the clerk of the court to the amount of damages, at the contract rate, if established, or at a rate calculated pursuant to the provisions of section six I from the date of the breach or demand. If the date of the breach or demand is not established, such interest shall be added by the clerk of the court from the date of the commencement of the action." Accessed 2026-10-06: https://malegislature.gov/Laws/GeneralLaws/PartIII/TitleII/Chapter231/Section6C
• Mass. Gen. Laws ch. 231, § 6I — "Interest required to be paid by the commonwealth pursuant to this section shall be calculated at a Weekly average one-year constant maturity Treasury yield, as published by the Board of Governors of the Federal Reserve System, for the calendar week preceding date of the judgment; provided, however, that such interest shall not exceed the rate of ten percent per annum. The secretary of administration and finance shall maintain a schedule of the rate described above for the distribution to all clerks of courts." Accessed 2026-07-05: https://malegislature.gov/Laws/GeneralLaws/PartIII/TitleII/Chapter231/Section6I
• Mass. Gen. Laws ch. 258, § 2 — "Public employers shall be liable for injury or loss of property or personal injury or death caused by the negligent or wrongful act or omission of any public employee while acting within the scope of his office or employment, in the same manner and to the same extent as a private individual under like circumstances, except that public employers shall not be liable to levy of execution on any real and personal property to satisfy judgment, and shall not be liable for interest prior to judgment or for punitive damages or for any amount in excess of $100,000; provided, however, that all claims for serious bodily injury against the Massachusetts Bay Transportation Authority shall not be subject to a $100,000 limitation on compensatory damages." Accessed 2026-07-05: https://malegislature.gov/Laws/GeneralLaws/PartIII/TitleIV/Chapter258/Section2
• Greene v. Philip Morris USA Inc. (Mass. Supreme Judicial Court, decided May 9, 2023) — rejected a due-process challenge to the fixed 12% prejudgment (and postjudgment) interest rates, holding they survive rational-basis review. Verified via legalresearch (courtlistener id 9397610); cited elsewhere as 491 Mass. 866 (2023).
• MA H.1795 / S.1149 (194th General Court, 2025-2026) — would replace the fixed 12% rate in §§ 6B and 6C with a floating Treasury-yield rate; both companion bills received a study order (S.1149 on 2026-01-29, H.1795 on 2026-03-26) without a floor vote. Accessed 2026-10-06: https://malegislature.gov/Bills/194/S1149