The Collateral Source Rule, Explained

The collateral source rule is a common-law rule with two parts. As a rule of damages, it bars a defendant from reducing the plaintiff's compensatory award by the amount the plaintiff received from a collateral source; as a rule of evidence, it keeps the jury from learning about that compensation (Legal Information Institute, 2024; Wills v. Foster, 2008). The Restatement (Second) of Torts states the damages part in words state courts quote: "Payments made to or benefits conferred on the injured party from other sources are not credited against the tortfeasor's liability, although they cover all or a part of the harm for which the tortfeasor is liable" (American Law Institute, 1979; Wills v. Foster, 2008). On the evidence side, the rule prevents a defendant from informing the jury that the plaintiff has already been compensated by private insurance (Legal Information Institute, 2024).

One justification courts give comes from the Restatement's commentary: "a benefit that is directed to the injured party should not be shifted so as to become a windfall for the tortfeasor" (American Law Institute, 1979; Wills v. Foster, 2008); another, often cited, is that the tortfeasor should not benefit from expenditures the injured party made in procuring insurance (Wills v. Foster, 2008). The result can be that a plaintiff receives more than total compensation, as New Jersey's model jury charge says of the common-law rule (New Jersey Courts, 2021), although the Illinois Supreme Court agreed with the appellate court that the collateral source will typically have a lien or subrogation right that prevents a double recovery (Wills v. Foster, 2008). The Restatement's commentary also notes that the rule is of common-law origin and may be altered by statute (Wills v. Foster, 2008), and the states described below have altered it.

Any source of payment or benefit that is independent of the defendant. The Illinois Supreme Court describes benefits received "from a source wholly independent of, and collateral to, the tortfeasor" (Wills v. Foster, 2008), and the California Supreme Court states the rule in the same terms (Howell v. Hamilton Meats & Provisions, Inc., 2011). A payment by the defendant, or by someone acting for the defendant, is not collateral: the Restatement's commentary says the law does not differentiate between the nature of the benefits "so long as they did not come from the defendant or a person acting for him" (American Law Institute, 1979; Wills v. Foster, 2008). The same commentary lists four kinds of collateral benefits (Wills v. Foster, 2008):

• insurance policies;
• employment benefits;
• gratuities, so that a plaintiff whose doctor did not charge, or who was treated in a veterans hospital, may still recover the reasonable value of the services (Wills v. Foster, 2008); and
• social legislation benefits, such as a disability pension under the Railroad Retirement Act, which the U.S. Supreme Court, quoting an appeals court, described as a system of social legislation (Eichel v. New York Central Railroad Co., 1963).

A statute that modifies the rule may write its own list. Connecticut's statute defines collateral sources as payments under health or sickness insurance, automobile accident insurance that provides health benefits and similar insurance other than life insurance, or under a contract to provide, pay for or reimburse the cost of hospital, medical, dental or other health care services, and it leaves out amounts received as a settlement (Connecticut General Assembly, 2025).

Generally not: as a rule of evidence, the collateral source rule keeps the jury from learning that an insurer or another source has paid (Wills v. Foster, 2008). The U.S. Supreme Court, upholding the exclusion of evidence of a railroad worker's disability pension at the trial of his injury suit, reasoned that "the likelihood of misuse by the jury clearly outweighs the value of this evidence" (Eichel v. New York Central Railroad Co., 1963). The exclusion has limits. Collateral source evidence may be admitted to rebut testimony that the plaintiff paid the bills personally (Legal Information Institute, 2024). In Massachusetts it may be admitted if probative of a relevant issue, such as impeaching the plaintiff's credibility or showing motive; the amounts a health insurer actually paid are redacted from medical bills admitted into evidence, and the court may instruct the jury that any amounts paid by insurance are subject to recoupment by the payor (Massachusetts Court System, Trial Court Law Libraries, 2026). A federal appeals court upheld admitting a health insurer's payments after the injured child's mother, herself a plaintiff, testified that the medical bills were a source of financial strain, concluding that the plaintiffs had opened the door (Fitzgerald v. Expressway Sewerage Construction, Inc., 1999).

Where New York, New Jersey or Connecticut reduces an award by statute, the court, not the jury, makes the reduction once damages are awarded. New York's statute has the trial court make the deduction after the jury's verdict and lets the plaintiff prove the losses at trial whether or not they will later be deducted (Admissibility of collateral source of payment, 2026); New Jersey's model charge for non-automobile cases has the jury consider the full amount of the medical bills incurred and the court make any required adjustment afterward (New Jersey Courts, 2021); and Connecticut's statute has the court receive the collateral source evidence after the finding of liability and before it enters judgment (Connecticut General Assembly, 2025).

New York, New Jersey, Connecticut and Massachusetts each change it by statute, and the versions differ on which payments count, which cases they reach and what is credited back for the cost of the coverage. Each is stated below in the state's own terms, as its legislature or courts publish it, read on October 19, 2026:

• New York. In an action for personal injury, injury to property or wrongful death, evidence is admissible for the court to consider that a past or future cost of medical, dental or custodial care or rehabilitation services, lost earnings or another economic loss was or will, with reasonable certainty, be replaced or indemnified from a collateral source, other than life insurance and payments that carry a statutory right of reimbursement. If the court so finds, it reduces the award by that amount, minus the premiums the plaintiff paid for the benefits in the two years before the action accrued and minus the projected future cost to the plaintiff of keeping them. Voluntary charitable contributions are not a collateral source for this purpose (Admissibility of collateral source of payment, 2026).
• New Jersey. The state's collateral source statute, as the New Jersey Supreme Court quotes it, applies in any civil action brought for personal injury or death, except actions brought pursuant to the automobile no-fault law: benefits the plaintiff receives or is entitled to receive for the injuries from any source other than a joint tortfeasor, other than workers' compensation benefits or the proceeds of a life insurance policy, are disclosed to the court, and the amount that duplicates any benefit contained in the award is deducted from it, less any premium paid to an insurer directly by the plaintiff or by any member of the plaintiff's family on the plaintiff's behalf for the policy period during which the benefits are payable (Perreira v. Rediger, 2001). The courts' model jury charge on medical expenses in non-automobile cases says the common-law rule "has been severely limited by a number of statutes." It applies the statute's reduction to personal injury and wrongful death actions arising after December 18, 1987, and lists the automobile no-fault law, the uninsured and underinsured motorist statute, the Tort Claims Act and the Workers' Compensation Act among the statutes that limit the rule (New Jersey Courts, 2021).
• Connecticut. In a civil action, whether in tort or in contract, for a personal injury or wrongful death occurring on or after October 1, 1987, the court reduces the economic damages awarded by the collateral sources paid for the claimant's benefit as of judgment, less the amounts paid, contributed or forfeited to secure them, and it makes no reduction for a collateral source for which a right of subrogation exists. When the court takes that evidence, after the award and before judgment, proof that a physician or another practitioner the statute lists accepted less than the full bill, or that an insurer paid less, is admissible as evidence of the collateral sources paid (Connecticut General Assembly, 2025).
• Massachusetts. Evidence of collateral source payments is generally not admissible to reduce damages, and two statutes reduce the verdict instead. In most motor vehicle cases the verdict is reduced by the personal injury protection benefits the plaintiff received. In a medical malpractice case, the defendant may show the court, at a post-verdict hearing, the medical bills covered by insurance, which are deducted from the itemized verdict less the plaintiff's premiums for the year before the cause of action accrued, a procedure that does not apply to a payor with subrogation rights based on federal law (Massachusetts Court System, Trial Court Law Libraries, 2026).

These four are examples, not a survey, and a statute can be amended after the date it was read. Attorneys confirm the governing rule for their case.

Through repayment rights of their own, which act on the recovery rather than on the damages figure. Medicare does not pay for items or services to the extent that payment has been, or may reasonably be expected to be, made by a liability or no-fault insurer or a workers' compensation entity; it may make a conditional payment when there is evidence that such a primary plan does not pay promptly, conditioned on reimbursement, and its Benefits Coordination & Recovery Center recovers conditional payments when there is a settlement, judgment, award or other payment to the beneficiary (Centers for Medicare & Medicaid Services, 2024). These rules come from the Medicare Secondary Payer provisions of the Social Security Act (Medicare Secondary Payer provisions, 2018). For Medicaid, the U.S. Supreme Court held that a state's assigned rights in a beneficiary's tort settlement extend only to recovery of payments for medical care, so its lien could not reach the portions meant for nonmedical damages such as lost wages (Arkansas Department of Health and Human Services v. Ahlborn, 2006), and later that the Medicaid Act permits a state to seek reimbursement from settlement payments allocated for future medical care (Gallardo v. Marstiller, 2022).

The damages side belongs to the forum's rule. The Illinois Supreme Court held that a plaintiff whose bills Medicare and Medicaid settled for less than the billed amounts could seek the reasonable value of her medical expenses and was not limited to the amounts those programs paid (Wills v. Foster, 2008), while New York's statute makes no reduction for payments that carry a statutory right of reimbursement (Admissibility of collateral source of payment, 2026).

The rule matters in a case whenever someone other than the defendant has already paid for part of the loss. Medical expense is the clearest example: a health insurer paid the providers at negotiated rates, and the question is whether the plaintiff recovers the amount billed, the amount paid, or the amount paid less what the insurer will take back. Courts answer it differently. Surveying the case law in 2008, the Illinois Supreme Court described three approaches: recovery limited to the amount actually paid; a benefit-of-the-bargain approach that allows recovery of the full bill where the plaintiff paid some consideration for the benefit of the write-off; and reasonable value, which it said most courts follow, the vast majority of them letting the plaintiff seek the amount originally billed (Wills v. Foster, 2008). Illinois follows the reasonable-value approach (Wills v. Foster, 2008). The California Supreme Court held that a plaintiff whose medical expenses are paid through private insurance may recover as economic damages no more than the amounts paid by the plaintiff or the insurer for the services received or still owing at the time of trial, and said that in so holding it did not abrogate or modify the collateral source rule, because the negotiated rate differential is not a benefit provided to the plaintiff in compensation for the injuries (Howell v. Hamilton Meats & Provisions, Inc., 2011). In Massachusetts the full bill is admissible as evidence of the reasonable value of the services even where an insurer paid less, the amount insurance actually paid is not, and the defendant may offer evidence of the range of payments the provider accepts for that service (Massachusetts Court System, Trial Court Law Libraries, 2026).

The same question arises for the earnings loss where a workers' compensation carrier or a long-term disability insurer has paid wage benefits, and Medicare and Medicaid carry the repayment rights described above. In each case the forum's version of the rule decides whether the payment is subtracted from the damages figure, and a lien decides how much of the figure the plaintiff keeps. Attorneys confirm the governing rule for their case.

Before the economist is asked to prepare the schedule, five questions are settled with counsel, and their answers go into the engagement letter. Which version of the rule applies in the forum, and does it treat medical payments, wage benefits and disability benefits alike or category by category? Which payers have made payments on account of the injury, and has each produced a statement of what it paid, such as an explanation of benefits, a carrier's payment ledger or Medicare's conditional payment letter, or only of what was billed? Has any payer asserted a lien or a right of reimbursement, and under what document? Are any of the payments expected to continue, so that a future stream has to be projected on the offset side as well as the loss side? And does the forum reduce an offset by the premiums the plaintiff paid for the coverage? Each answer changes a row of the schedule or the footing of the net figure, and an answer that is still open is recorded in the report as an assumption rather than resolved by the economist. Attorneys confirm the governing rule for their case.

Both figures: gross damages computed as if no collateral payment existed, and net damages under the offset counsel identifies. A forensic economist's report handles the rule by showing the computation both ways rather than by choosing. The gross figure comes first. Beneath it is a schedule of the collateral payments identified in the record, one line per source, with the period and the documented amount, drawn from benefit statements, carrier ledgers and program conditional payment records. The net figure follows, with each subtracted line traceable to the schedule. Future benefits that are expected to continue are projected and discounted to present value on the same footing as the losses they offset. A closing note lists liens and reimbursement claims and their basis, apart from the damages, so counsel can see the likely net recovery. The report does not decide which figure the law requires; it makes both available so the court can apply the rule it finds governs.

A hypothetical makes the arithmetic concrete; its figures are illustrative and drawn from no actual matter. Providers billed $40,000 for past care, and a health insurer paid $16,000, which the providers accepted as payment in full; a disability insurer paid $9,000 against a past wage loss of $30,000. Measured on the billed amounts, gross damages are $70,000. Net of the health insurer's payment they are $54,000, and net of both payments $45,000. Those two rows keep the $24,000 the providers wrote off; where the forum's offset also removes the write-off, the medical line falls to zero and the two net figures are $30,000 and $21,000. In a forum that measures past medical expense by the amounts paid, the medical line starts at $16,000 and gross damages are $46,000. The schedule shows each of those rows, and the closing note lists any reimbursement claim either insurer has asserted.

Kincaid Wolstein Vocational and Rehabilitation Services (KWVRS) provides forensic economic analysis with its affiliated firm, Kincaid Wolstein Economics, for plaintiff and defense counsel, and the report presents both figures whichever side retains it. The collateral source analysis method page describes the computation and the records behind each row.