In Tennessee breach of contract cases, the defense of unilateral mistake falls in the category of legal defenses (and claims) that are fairly often asserted, but rarely successful. Nevertheless, for lawyers who handle breach of contract cases in Tennessee, this is a defense that, in some cases, can be outcome determinative.
Tennessee contract law recognizes two categories of mistakes as defenses to breach of contract claims: (1) Mutual mistakes; and (2) unilateral mistakes. The defense of mutual mistake applies when both parties are mistaken as to a fact material to the contract. The unilateral mistake defense applies when only the party invoking the defense was mistaken.
Both defenses, mutual mistake and unilateral mistake, apply only to mistakes about facts that existed at the time the parties’ contract was formed. In situations where facts arise after the formation of the contract that a party believes may excuse it from performance of its obligations, that party should look to the doctrines of impracticability and frustration of purpose, but not to mistake.