mirror-image rule.Contracts. The doctrine that the acceptance of a contractual offer must be positive, unconditional, unequivocal, and unambiguous, and must not change, add to, or qualify the terms of the offer; the common-law principle that for a contract to be formed, the terms of an acceptance must correspond exactly with those of the offer. • In modern commercial contexts, the mirror-image rule has been replaced by a UCC provision that allows parties to enforce their agreement despite minor discrepancies between the offer and the acceptance. The rule still applies to international sales contracts governed by the UN Convention on Contracts for the International Sales of Goods (article 19). — Also termed ribbon-matching rule. See BATTLE OF THE FORMS . [Cases: Contracts 24. C.J.S. Contracts §§ 52–53.]
“If an offeree purports to accept an offer but in doing so adds various conditions and qualifications of his own, is the acceptance binding on the offeror, at least in part? Generally speaking, the answer is no: the common law rule, reflected in Restatement Section 59, is that a statement of acceptance is effective only if it is a mirror image of the offer and expresses unconditional assent to all of the terms and conditions imposed by the offeror.” Marvin A.
Chirelstein, Concepts and Case Analysis in the Law of Contracts 54 (1990).
[Blacks Law 8th]