Battle of the Forms: Whose Terms Govern a Purchase Order

A buyer sends a purchase order. The seller sends back an acknowledgement with different fine print. Nobody reads either one, the goods ship, and months later something goes wrong. Whose terms govern? For sales of goods, the answer comes from the state's enactment of UCC 2-207, which discarded the old rule that an acceptance had to match the offer exactly. A reply that adds or changes terms can still form a contract. Which of the added terms survive depends on whether both sides are merchants, whether the terms materially alter the deal, and on state law that is genuinely split.

1.What replaced the mirror image rule

Under common law, an acceptance had to mirror the offer. Any variation was a counteroffer, which meant the last form sent before performance became the contract — the last shot rule.

Article 2 changed this for goods. A definite and seasonable expression of acceptance operates as an acceptance even though it states terms additional to or different from those offered. The contract forms on the reply. What the reply added is then handled as a separate question, and that separation is the design of the section. The text is at Cornell LII on UCC 2-207, and the model language each state enacted comes from the Uniform Law Commission.

There is one escape hatch. If the reply is expressly made conditional on the other side's assent to the new terms, it is not an acceptance. It is a counteroffer, and common law logic returns. Courts read that exception narrowly; boilerplate saying the seller "objects to any different terms" is generally not enough.

2.Whether the extra terms stick

Once a contract has formed on the reply, additional terms are treated as proposals. If either party is not a merchant, they do not become part of the contract unless the other side actually agrees. Between merchants the default flips: additional terms join automatically unless one of three conditions applies.

• The offer expressly limited acceptance to its own terms — the single most effective line a buyer can put on a purchase order.
• The additional terms materially alter the contract.
• Notice of objection to them has already been given, or is given within a reasonable time after notice of them is received.

Material alteration is the fight. The test generally asked is whether the term would cause surprise or hardship if incorporated without express awareness. Terms routinely litigated as material alterations include arbitration clauses, disclaimers of the implied warranties of merchantability and fitness, limits on consequential damages, shortened periods for bringing suit, indemnity obligations, and clauses fixing venue in the seller's home state.

The results are not uniform. Some states treat an arbitration clause as a material alteration almost per se; others ask whether arbitration is customary in that trade and refuse to assume surprise. Warranty disclaimers face an added hurdle regardless of 2-207, because the state's version of UCC 2-316 imposes its own conspicuousness and language requirements, as covered in warranty disclaimers in business-to-business sales.

Caution: Do not assume industry custom saves a term. Whether a clause causes unfair surprise is decided on the record in a particular case and a particular state, and the same arbitration clause has been held both a material alteration and an unsurprising trade norm in different jurisdictions.

3.Different terms and the state split

An additional term addresses a subject the offer left alone. A different term contradicts one the offer already covered — the order says the seller carries all risk of loss, the acknowledgement says risk passes at the dock. The statute does not clearly say what happens to different terms, and courts have gone three ways. Which approach applies is a matter of state law.

Knock-out approach

Conflicting terms cancel each other and drop out. The gap is filled by the state's default rules under Article 2. This is the most widely followed approach, and it means neither side's clause governs.

Treat as additional

Different terms are run through the same material alteration analysis as additional ones. Because a term that contradicts the offer will nearly always be a material alteration, the offeror's term usually survives.

Drop-out approach

The differing term in the reply simply falls away and the offeror's term controls, with no material alteration inquiry at all.

The choice matters most where the default rule is worse for one side than either form. Under the knock-out approach, a seller who disclaimed the implied warranties, against a purchase order expressly demanding them, may end up with the statutory warranties applying in full — the outcome neither form wanted. That is a clear reason to confirm the governing state early, using the analysis in choice of law and forum selection.

4.When conduct makes the contract

Sometimes the writings never form a contract at all. The acknowledgement was properly conditional, or the forms diverge so completely that no acceptance can be found. Then the goods ship, the buyer pays, and both sides have plainly behaved as though a deal exists. Subsection three handles that situation. Conduct by both parties recognizing a contract establishes one, and the terms are limited to those on which the writings agree, together with supplementary terms supplied by the rest of Article 2. Everything disputed falls out.

Notice the pattern. A seller whose acknowledgement is drafted as an aggressive counteroffer may win the formation argument and lose every protective term it cared about. That is why sophisticated sellers often prefer a plain acceptance with carefully chosen additions over a conditional one.

Where the arrangement is an ongoing supply relationship rather than a single order, the problem compounds across dozens of transactions, and the quantity questions discussed in requirements and output contracts arrive on top of it. Signed master agreements exist to shut this down, and the practices addressed in electronic signatures under ESIGN and UETA determine whether the signed version can be proved later.

5.Questions this raises

Does putting "these terms govern" on the purchase order settle it?

It helps considerably. An offer that expressly limits acceptance to its own terms blocks additional terms from joining automatically between merchants, which is one of the three listed conditions. It does not resolve conflicting terms, since that depends on which of the three state approaches applies. And it does nothing if the buyer later signs the seller's document or performs after a properly conditional counteroffer.

Our acknowledgement says acceptance is expressly conditional. Are we protected?

Only if the language is clear enough. Courts read that exception narrowly and generally require wording showing the seller will not proceed without assent to its terms, not a general objection buried in boilerplate. Even where the clause works, it makes the acknowledgement a counteroffer, and if the buyer never assents and the goods simply ship, the conduct provision may strip the very terms the clause was protecting.

Does 2-207 apply when we send an invoice after a phone order?

Yes, in a different posture. A written confirmation sent within a reasonable time after an oral agreement is covered by the same section, and additional terms in it are treated as proposals. Between merchants they can join the contract subject to the same three conditions. Terms first appearing on an invoice after performance are frequently held to be material alterations, though this varies.

What if the deal is mostly installation and only partly equipment?

Then classification comes first. Article 2 and 2-207 reach sales of goods. A mixed contract is usually classified by its predominant purpose, and if services predominate, state common law governs, which means the mirror image rule and last shot rule return. The classification test differs by state, so a contract that is a goods contract in one state may not be in another.

6.What to do on a disputed order

1. Assemble the paper in order. Quote, purchase order, acknowledgement, confirmation, invoice, packing list. Note when each was sent and received, because the sequence decides which document is the offer.
2. Classify the contract. Confirm the deal is predominantly for goods. If services predominate, the analysis changes entirely.
3. Find the governing state. Read its enacted version of the section rather than the model text, and check whether it follows the knock-out approach.
4. Test the acknowledgement. Determine whether it was a plain acceptance or genuinely expressly conditional, using that state's standard.
5. Sort the extra terms. Separate additional from different, then run the additional ones through the merchant conditions.
6. Object in writing. Timely written objection is itself one of the three conditions that keeps a term out.

For prevention, the durable fix is not a better form. It is a signed master agreement stating that it controls over any purchase order or acknowledgement, with individual orders limited to quantity, price, and delivery. Absent that, the buyer's most useful line is an express limitation of acceptance to the order's own terms, and the seller's is a short, prominent set of terms rather than a long unread appendix.

General small business contracting guidance is published by the U.S. Small Business Administration, and the Federal Trade Commission's business guidance covers related advertising and warranty obligations. The sales rules sit in Article 2, as enacted with variations in each state. Because the split on different terms remains unresolved as of mid-2026, the governing state is the first thing to establish and the last thing to assume.