Acceptance

Formation has two halves. An offer confers a power of acceptance; acceptance is the act that completes the manifestation of mutual assent and turns the offer into a contract. This class asks three questions about that act: what counts as an acceptance, when does it take effect, and what happens when the offeree’s response does not exactly match the offer? The common law answers the last question with the strict mirror-image rule; the UCC answers it, for sales of goods, with § 2-207. The two regimes can reach opposite results on the same facts, so the first move in any acceptance problem is to ask which body of law governs.

What counts as acceptance

R2d § 50. Acceptance of an offer is a manifestation of assent to the terms of the offer, made by the offeree in a manner invited or required by the offer. Acceptance by performance requires that at least part of what the offer requests be performed or tendered; acceptance by promise requires the offeree to complete every act essential to making the promise. The offeror is the master of the offer and may dictate the mode and manner of acceptance, but where the offer is silent, any reasonable medium will do.

The mirror-image rule and its limits

R2d § 58. An acceptance must comply with the requirements of the offer as to the promise to be made or the performance to be rendered. At common law this is the mirror-image rule: any deviation makes the response a counter-offer that rejects and terminates the original offer. But the rule has limits. An acceptance that merely adds collateral or immaterial matter, or that states only what was already implied in the offer, is still an acceptance. The line is materiality: a response converts into a counter-offer only when it differs from the offer in some material respect, or when it makes assent conditional on new terms.

Timing: the mailbox rule

R2d § 63. Unless the offer provides otherwise, an acceptance sent by an invited medium is operative as soon as it leaves the offeree’s possession, whether or not it ever reaches the offeror. Acceptance is effective on dispatch; revocations, rejections, and counter-offers are effective only on receipt. The dispatch rule does not apply to acceptances under an option contract, which are operative only when received. Where an offeree sends a rejection first and then an acceptance, whichever the offeror receives first controls.

Acceptance for the sale of goods

UCC § 2-207. For sales of goods, Article 2 rejects the mirror-image rule. A definite and seasonable expression of acceptance operates as an acceptance even though it states terms additional to or different from the offer, unless acceptance is expressly made conditional on assent to those terms. This is the gateway to the battle of the forms, which Class 10 walks in full. Today’s job is to see the contrast: the same exchange that fails as an acceptance under R2d § 58 can form a contract under § 2-207(1).

Cases

Flender Corp. v. Tippins International is the canonical knockout case. Tippins’s purchase order demanded arbitration in Vienna; Flender shipped the goods and sent an invoice demanding litigation in Chicago. The Pennsylvania Superior Court held that Flender’s invoice was a definite acceptance forming a contract under § 2-207(1), because Flender never made the deal conditional on its own terms. But the two conflicting dispute-resolution clauses both dropped out under the knockout rule, leaving background jurisdictional law to govern. State Department of Transportation v. Providence & Worcester Railroad shows the mirror-image rule’s limit. The State accepted P&W’s offer to sell rail land but noted that the buyer’s name had to change and that P&W’s track-removal obligation was inappropriate. The Rhode Island Supreme Court held this a valid acceptance: putting into words what the offer already implied, and relieving the offeror of a burden, adds no material term and does not turn an acceptance into a counter-offer. Read together, the cases mark the boundary between immaterial variations that leave acceptance intact and conflicting terms that trigger the UCC knockout.

What you should be able to do

Apply R2d § 50 to decide whether an offeree has accepted by performance or by promise, and recognize the offeror as master of the manner of acceptance. Apply the mirror-image rule (R2d § 58) on a common-law fact pattern, sort material deviations (counter-offers) from immaterial additions (still acceptance, as in State DOT), and explain how the result changes if Article 2 governs. Apply the mailbox rule (R2d § 63) to an acceptance-then-rejection or rejection-then-acceptance sequence and determine which controls. And state why Flender forms a contract but enforces neither party’s forum clause. Class 10 turns § 2-207 into a working decision tree and runs a full battle-of-the-forms exchange through every branch.