reformation
Reformation is an equitable remedy that changes the language of an instrument so it accurately expresses the agreement the parties actually reached. It is used when a contract, deed, insurance policy, or other legal document fails to reflect that prior agreement due to a mistake or certain forms of fraud. Reformation corrects the writing; it does not create a new agreement simply because the original terms were harsh or later became inconvenient.
A common basis is mutual mistake, where both parties shared an agreement or understanding but the final writing misstated or omitted it, including through a drafting or scrivener's error. In Snell v. Insurance Co., 98 U.S. 85 (1878), the U.S. Supreme Court recognized equitable power to reform an insurance policy that, because of mutual mistake, did not express the parties' earlier agreement. Some jurisdictions also permit reformation for a unilateral mistake when the other party knew or suspected the mistake, caused it through fraud, or engaged in inequitable conduct. California Civil Code § 3399, for example, authorizes revision for fraud, mutual mistake, or one party's mistake known or suspected by the other, while protecting rights acquired by third persons in good faith and for value.
Because reformation alters a signed writing, the party requesting it ordinarily must prove the prior agreement and the mistake with clear and convincing or similarly heightened evidence. The requested correction must be definite enough for the court to identify the terms that should appear in the instrument. For example, in P.S. Marcato El. Co., Inc. v. Scottsdale Ins. Co., 249 A.D.3d 472 (N.Y. App. Div. 2026), the Court required positive, clear and convincing evidence and rejected mutual-mistake reformation because the record did not establish the alleged prior oral agreement. Reformation may be denied if the evidence shows only that one party misunderstood an unambiguous deal.
Reformation differs from interpretation, rescission, and modification. Interpretation determines what existing language means. Rescission seeks to fully cancel the transaction. Modification changes the parties' obligations by a later agreement. Reformation instead conforms the written instrument to the parties' antecedent agreement, subject to the governing law and protected third-party rights.
Courts also consider defenses and third-party interests. Unreasonable delay, acquiescence, laches, waiver, or prejudice may bar relief. Reformation ordinarily cannot prejudice rights acquired by a third party in good faith and for value, such as the rights of a bona fide purchaser without notice. Because the available grounds, proof standards, limitation periods, and effects on third parties vary by jurisdiction, a reformation claim must be evaluated under the law governing the instrument.
[Last reviewed in August of 2026 by the Wex Definitions Team]
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