Contract law: Contract formation - Firm offer, Invitation to bargain and Mirror image rule

A firm offer is an offer that will remain open for a certain period or until a certain time or occurrence of a certain event, during which it is incapable of being revoked. As a general rule, all offers are revocable at any time prior to acceptance, even those offers that purport to be irrevocable on their face.

In the United States, an exception is the merchant firm offer rule set out in Uniform Commercial Code - § 2-205, which states that an offer is firm and irrevocable if it is an offer to buy or sell goods made by a merchant and it is in writing and signed by the offeror. Such an offer is irrevocable even in the absence of consideration. If no time is stated, it is irrevocable for a reasonable time, but in no event may a period of irrevocability exceed three months. Any such term of assurance in a form supplied by the offeree must be separately signed by the offeror.

However, even when the period of irrevocability expires, the offer may still remain open until revoked or rejected according to the general rules regarding termination of an offer.

If the offeree rejects, fails to accept the terms of the offer, fixed or otherwise, or makes a counteroffer, then the original offer is terminated.

In the law of contracts, the mirror image rule, also referred to as an unequivocal and absolute acceptance requirement, states that an offer must be accepted exactly with no modifications. The offeror is the master of their own offer. An attempt to accept the offer on different terms instead creates a counteroffer, and this constitutes a rejection of the original offer.

United States

In the United States, this rule still exists at common law. However, the Uniform Commercial Code ("UCC") dispenses with it in § 2-207. (but it can also be argued that § 2-207(1) enforces the mirror image rule) Therefore, its applicability depends upon what law governs. Most states have adopted the UCC, which governs transactions in goods. Contracts for services or land, for example, would not be governed by the UCC. The 2nd restatement of contracts also provides that when parties have not agreed to an essential term, "a term which is reasonable in the circumstances is supplied by the court." However, it may not be possible for a reasonable term to be supplied by the court.

An invitation to treat (or invitation to bargain in the United States) is a concept within contract law which comes from the Latin phrase invitatio ad offerendum, meaning "inviting an offer". According to Professor Andrew Burrows, an invitation to treat is:

"...an expression of willingness to negotiate. A person making an invitation to treat does not intend to be bound as soon as it is accepted by the person to whom the statement is addressed."

A contract is a legally binding voluntary agreement formed when one person makes an offer, and the other accepts it. There may be some preliminary discussion before an offer is formally made. Such pre-contractual representations are known variously as “invitations to treat”, “requests for information” or “statements of intention”.