Contracts: The Battle of the Forms.

Under the common law of contracts (ie, those contracts involving services rather than the sale of goods), the "mirror image rule" applies. In other words, if the offeror makes an offer to the offeree then the offeree can only accept that offer by mirroring the terms offered by the offeror. If not mirrored, then there has been a counter-offer rather than an acceptance.

But all that changes under the UCC. Under the UCC, the "mirror image rule" is abandoned. This means that if the contract is one in which the subject matter is the sale of goods, then it's possible that the offeree can accept on terms that are different from the terms offered or add additional terms to those that were offered, and those additional or different terms might be included in the contract as an acceptance to the offer rather than as a counter-offer. To determine whether, under the UCC, these additional or different terms are included, you must analyze as follows:

First determine whether the parties contracting are merchants. If either party is a non-merchant then analyze as above as if it were the common law with the "mirror image rule."

But, let's now assume the contract is between merchants. If the offeror and the offeree are merchants, and the offeree attempts to add additional terms to the offer, those terms will become part of the contract unless they materially alter the contract, or if the offeror had expressly limited acceptance to his terms, or if the offeror objects to the additional terms within a reasonable time after the offeree added them.

Assume, again, that the contract is between merchants, but this time, rather than adding additional terms, the offeree attempts to add different terms from those offered such that these different terms actually contradict the terms offered. In such a situation, there is a split of authority over whether these different terms in the acceptance become a part of the contract. Some courts treat different terms as they treat additional terms and will allow them in with exception. Other courts follow what has been called the "knockout rule." This rule states that conflicting terms in the offer and acceptance are knocked out of the contract and the terms instead are provided by the UCC.