Mirror Image Rule

The mirror image rule is a contract law principle requiring that an acceptance match the terms of an offer exactly, with no additions or changes, in order to form a contract. If a party purports to accept an offer while proposing different terms, that response is treated not as an acceptance but as a counter-offer, which rejects the original offer and leaves the original offeror free to accept or reject the new terms in turn. The rule grew out of the development, within English common law, of the ideas of offer, acceptance, and consensus ad idem, or a meeting of the minds, and the 1840 case Hyde v Wrench is the leading authority establishing that a counter-offer extinguishes the original offer; the principle remains recognized in later cases such as Gibson v Manchester City Council in 1979, even though English lawyers rarely use the phrase mirror image rule itself. The rule still applies in common law systems such as England and Australia, but in the United States the Uniform Commercial Code relaxes it, in Section 2-207, for contracts involving the sale of goods.