An offer may be accepted by either express or implied means of communication. In an express acceptance, the offeree may choose any method of acceptance, unless the offer states that it must be made in a particular manner. A stipulation such as «reply by Federal Express» or «reply by certified mail» in the offer must be carried out to complete an acceptance.
To be effective, an acceptance must be unequivocal, which means that the acceptance must not change any of the terms stated in the offer. Under common law, this stipulation is known as the mirror image rule.
Under the mirror image rule, the terms stated in the acceptance must duplicate the terms in the offer. If the acceptance changes or qualifies the terms in the offer, it is not an acceptance but a counteroffer. A counteroffer is a response to an offer in which the terms of the original offer are changed. No agreement is reached unless the counteroffer is accepted by the original offerer.
In contracts for the sale of goods, as long as there is a definite expression of acceptance, a contract will result even though an acceptance has different or additional terms. If both parties are not merchants, the different or additional terms are treated as proposals for amendment to the contract. If the parties are both merchants, however, the different or additional terms become part of the contract unless (a) they make an important difference, (b) the offerer objects, or (c) the offerer limits acceptance to its terms.
Acceptance may result from the conduct of the offeree. Actions and gestures may indicate the offeree's willingness to enter into a binding agreement.
As a general rule, silence is not an acceptance. If, however, both parties agree that silence on the part of the offeree will signal acceptance, then such an acceptance is valid.
Another exception to the general rule occurs when the offeree has allowed silence to act as acceptance. The offerer cannot force the offeree into a contract by saying silence will mean acceptance. The offeree, however, can force the offerer into a contract if the offerer established the silence condition.
A rejection comes about when an offeree expresses or implies refusal to accept an offer. Rejection terminates an offer and all negotiations associated with it. Further negotiations could commence with a new offer by either party or a renewal of the original offer by the offerer. Rejection is usually achieved when communicated by the offeree.
