Mutual Mistake Defense

A contract is voidable when both parties are mistaken about a basic assumption materially affecting the exchange.

Representative cases

• Reilley v. Richards 69 Ohio St. 3d 352 · Ohio Supreme Court
• Workers Compensation Fund v. Utah Business Insurance Co. 2013 UT 4 · Utah Supreme Court
• Hy-Vee Food Stores, Inc. v. Minnesota Department of Health 705 N.W.2d 181 · Supreme Court of Minnesota

Related Defenses to Formation rules

• Capacity to ContractMinors, mentally incompetent persons, and intoxicated individuals may avoid contracts due to lack of capacity.
• Misrepresentation DefenseContracts induced by material misrepresentation are voidable when justifiably relied upon.
• Fraud DefenseFraudulent inducement renders a contract voidable; fraud in factum may render it void.
• Duress DefenseDuress exists when an improper threat leaves no reasonable alternative.
• Undue Influence DefenseUndue influence arises from unfair persuasion of a vulnerable party by someone in a dominating position.
• Unilateral Mistake DefenseUnilateral mistake permits avoidance when the other party knew or caused the mistake.
• UnconscionabilityA court may refuse enforcement of unconscionable terms based on unfair surprise or oppressive results.
• Statute of Frauds CategoriesThe SOF applies to marriage, year-or-more, land, executors, goods ≥ $500, and suretyship.

Part of Contracts on Core Legal Rules — foundational MBE-tested principles with primary-source citations.