Massachusetts: Prejudgment Interest Rules

The short answer

Massachusetts adds interest to a money judgment automatically, and at a rate
most other states abandoned decades ago: 12% a year, fixed by statute rather
than tied to any market benchmark. It applies whether you win on a contract
claim or a personal-injury, wrongful-death, or property-damage tort claim —
the rate is identical either way. What differs is the date the clock starts.
Because the interest often runs for years before a case reaches judgment, it
can add up to a substantial fraction of the total recovery, sometimes
approaching the size of the underlying damages award in a long-running case.

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
specifically, § 6C redirects to § 6I's own formula: the weekly average
one-year constant-maturity Treasury yield published by the Federal Reserve,
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

Nothing in § 6B or § 6C provides for compounding. Both describe a flat annual
percentage applied over the period from the accrual date to judgment, which
is simple interest — there's no statutory language calling for interest to be
calculated on previously accrued interest.

Claims against the government

This is where contract and tort diverge sharply. A contract judgment against
the commonwealth still gets interest, just at the lower, floating § 6I rate
(capped at 10%) instead of the standard 12%. 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, a
bill to replace the fixed 12% rate with a floating Treasury-yield rate (the
same approach § 6I already uses for the commonwealth) has been filed and
sent to a study order — a procedural parking spot that ends the bill's
progress for the session without an up-or-down vote — in every two-year
session since at least 2017-2018, under bill numbers S.887, S.1075, S.1029,
and now S.1149/H.1795.

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. A bill to switch to a
floating Treasury-yield rate has been introduced repeatedly but has never
gotten past committee.

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, but at a lower, floating rate under § 6I instead of
12%. A tort claim against a public employer earns no prejudgment interest at
all under the Tort Claims Act.

Does the interest compound?
No. Both § 6B and § 6C describe a flat annual percentage with no 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 2026-07-05:
  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 2026-07-05:
  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 2026-07-05:
  https://malegislature.gov/Bills/194/S1149