The mirror image rule and its application to contract law states that an offer and an acceptance must mirror each other or else no contract is formed.
Under the common law mirror image rule, in order for a contract to be formed, an acceptance of an offer must be absolute, unconditional, and identical with the terms of the offer. If a person makes an offer and the person to whom the offer is made accepts conditionally or introduces a new term into the acceptance, this amounts to a rejection of the offer and serves as a counter offer which must be accepted before a contract can result.
The Uniform Commercial Code (the U.C.C.) has relaxed the formality of the common law mirror image rule when merchants are dealing in goods. The U.C.C. allows for the formation of a contract where an acceptance contains additional terms to the offer. These additional terms are construed as proposals for addition to the contract and become terms of the contract unless the offer expressly limits acceptance to the terms of the offer, the additional terms materially alter the offer, or notification of objection to the additional terms has been given or is given within a reasonable time after received.
While such an acceptance would not meet the strict requirements of the common law mirror image rule, the U.C.C. provides a more flexible approach to the formation of contracts so as to facilitate commercial transactions involving merchants dealing in goods.

