At common law, an acceptance had to mirror the offer exactly; any variation turned the reply into a counteroffer rather than an acceptance. That rule fit poorly with how merchants actually transact -- exchanging a purchase order and an order acknowledgment, each printed with its own boilerplate terms on the back, that rarely match line for line. UCC 2-207 replaces the mirror-image rule for these exchanges: a definite and seasonable expression of acceptance, or a written confirmation, forms a contract even if it states additional or different terms, unless the acceptance is made expressly conditional on the offeror's assent to those different or additional terms.

The provision matters because it decides, after the parties have already been performing for weeks or months, whose boilerplate actually governs -- arbitration clauses, warranty disclaimers, limitation-of-liability language, and forum-selection clauses routinely turn on this analysis.

Under UCC 2-207(1), a reply that is a definite and seasonable expression of acceptance forms a contract notwithstanding additional or different terms, unless it is expressly conditioned on assent to those terms. An offeree wanting to avoid automatic formation under mismatched terms must make that conditionality explicit and unmistakable -- boilerplate reciting 'subject to terms on the reverse' is often not enough on its own.

Where both parties are merchants, UCC 2-207(2) treats additional terms in the acceptance as proposals that become part of the contract unless they materially alter the deal, the original offer expressly limited acceptance to its own terms, or the offeror objects within a reasonable time. For terms that directly conflict rather than merely add something new, most courts apply the 'knockout rule': the conflicting terms cancel each other out and the UCC's own gap-filler provisions supply the missing term, though a minority of courts instead give the offer's term priority.

Litigation typically starts with sequencing -- which document was the offer, which was the acceptance, and whether either party is a merchant. From there the fight moves to materiality: courts commonly treat arbitration clauses, broad warranty disclaimers, and unusual limitation-of-liability terms as materially altering the deal, which keeps them out absent express agreement, while minor terms like standard payment timing more easily slip in. A party can also invoke course of dealing between the parties to argue a disputed term was, or was not, part of their established practice.

The stakes of a battle-of-the-forms fight are often less about whether a contract exists at all -- performance usually confirms that it does -- and more about which specific clause governs a specific dispute, particularly arbitration and forum-selection terms that decide where the rest of the case will even be heard. Juricratic models the exchanged forms as a claim path with a terms-resolution node, with a dial for whether a given clause counts as materially altering and for each party's merchant status, so a user can see how exposure on a downstream clause -- like an arbitration or damages-limitation term -- shifts as those dials move.