To establish the existence of a unilateral mistake, a party must show (1) the mistake was of so great consequence that to enforce the contract as made would be unconscionable; (2) the mistake relates to a material feature of the contract; (3) the mistake was made in spite of the exercise of ordinary care; and (4) the parties can be placed in status quo in the equity sense, i.e., rescission must not result in prejudice to the other party except for the loss of his bargain. See James T. Taylor & Son, Inc. v. Arlington I.S.D., 160 Tex. 617, 335 S.W.2d 371, 373 (1960); Hayes v. E.T.S. Enterprises, Inc., 809 S.W.2d 652, 658 (Tex. App.–Amarillo 1991, writ denied). Other circumstances, such as the acts or knowledge of the parties, may influence the extension of equitable relief under a unilateral mistake theory.  This is not to be confused with mutual mistake.

Unilateral Mistake