When a supplier substitutes an item, your rights under the Uniform Commercial Code are strong: you can reject the entire shipment, accept all of it, or accept the conforming units and reject the rest. You can also buy replacements elsewhere and charge the supplier for the price difference. Which option makes sense depends on what your contract says, whether the supplier gave you notice before shipping the substitute, and how fast you act after the box arrives.
The Perfect Tender Rule Is Your Starting Point
Every state has adopted some version of the UCC, and it holds sellers to a strict standard called the perfect tender rule. If the goods delivered differ from the contract in any way, you can reject the whole delivery, accept the whole delivery, or accept some commercial units and reject the rest.1Cornell Law Institute. Uniform Commercial Code 2-601 – Buyer’s Rights on Improper Delivery “Any way” is literal. A different brand, a different model number, an unspecified color, a lower grade of material — all of it counts as non-conforming. The supplier doesn’t earn credit for sending something close.
You don’t have to prove the substitute is inadequate for your purposes. You agreed to a specific item, and the law holds the supplier to that agreement. If it isn’t what you ordered, it’s non-conforming, and that fact alone triggers your right to reject.
When the Contract Lets the Supplier Substitute
The perfect tender rule can be contracted around. Many suppliers include language in their terms permitting shipment of “equivalent” or “comparable” items when the original product is out of stock. If you agreed to terms containing that kind of clause, you may have waived strict compliance for that transaction. Check the purchase order, the sales confirmation, and any terms-and-conditions document you accepted at checkout or during onboarding. The clause doesn’t need to be prominent to bind you.
Not every substitution clause a supplier slips into a confirmation form is enforceable, though. When two businesses exchange forms with different terms, a new clause that materially changes the deal doesn’t automatically become part of the contract.2Cornell Law Institute. Uniform Commercial Code 2-207 – Additional Terms in Acceptance or Confirmation A broad right to substitute that wasn’t in your original purchase order can qualify as a material change, meaning the supplier can’t enforce it unless you separately agreed. If you’re a business buyer and the supplier’s confirmation introduced a substitution clause your PO never contained, you have a real argument the clause never took effect.
Past Dealing and Industry Custom
Even without a written clause, your history with a supplier can create an implied right to substitute. If you’ve accepted similar swaps from the same supplier more than once without objecting, a court may treat that pattern as a modification of your agreement going forward.3Cornell Law Institute. Uniform Commercial Code 1-303 – Course of Performance, Course of Dealing, and Usage of Trade Trade customs work the same way. If substituting equivalent materials is standard practice in your industry, that norm can fill gaps in your written contract. The practical takeaway: if you don’t want substitutions, object in writing the first time one happens. Silence builds a pattern that works against you later.
Accommodation Shipments
Sometimes a supplier sends a different item and explicitly tells you the shipment is offered as an accommodation because they can’t fill the original order. That notice changes the legal picture. Normally, shipping non-conforming goods in response to your order counts as the supplier accepting your offer and simultaneously breaching the contract. When the supplier flags the shipment as an accommodation, it doesn’t count as accepting your offer at all.4Cornell Law Institute. Uniform Commercial Code 2-206 – Offer and Acceptance in Formation of Contract The supplier is effectively saying, “I can’t get you what you ordered, but here’s an alternative if you want it.” You can keep the goods and pay, or send them back. The supplier isn’t in breach because no contract formed on the original terms. This only works if the supplier actually sends the accommodation notice before or alongside the shipment. A supplier who ships the wrong item without any notice and later calls it an accommodation will struggle to make that argument.
Consumer Orders by Mail, Phone, or Internet
If you ordered as a consumer rather than as a business, a separate layer of federal protection applies. The FTC’s Mail, Internet, or Telephone Order Merchandise Rule limits what a seller can do when it can’t ship your original order. A seller facing a backorder has two options: get your agreement to a delayed shipment, or give you a full refund. Substituting materially different merchandise without your express prior consent isn’t on the list.5Federal Trade Commission. Business Guide to the FTC’s Mail, Internet, or Telephone Order Merchandise Rule “Materially different” covers differences in design, color, fabric, style, or any feature the seller mentioned in its advertising.
Federal law also treats merchandise mailed to you without your prior request or consent as a gift. You can keep it, use it, or throw it away with no obligation to pay or return it.6Office of the Law Revision Counsel. 39 USC 3009 – Mailing of Unordered Merchandise Whether a particular substitute qualifies as unordered merchandise depends on the facts, but if you ordered a blue widget and the seller sent a red one you never agreed to, the argument has some teeth.
Act Fast or You’ll Lose the Right to Reject
The clock starts the moment the shipment arrives, and the single biggest mistake buyers make is waiting too long. Under the UCC, you’re deemed to have accepted goods in three ways: you inspect them and tell the seller they’re fine (or that you’ll keep them despite the problem); you fail to reject within a reasonable time after having a chance to inspect; or you do something inconsistent with the seller’s ownership, like reselling the goods or working them into your own product.7Cornell Law Institute. Uniform Commercial Code 2-606 – What Constitutes Acceptance of Goods
Acceptance matters because it narrows your options sharply. Once you’ve accepted, you can no longer reject. You can still pursue breach-of-warranty claims and damages, but you’ve lost the straightforward power to send everything back and refuse payment. Letting boxes sit unopened in your warehouse creates a strong inference that you accepted whatever was inside.
If you’ve already accepted, one route remains: revocation of acceptance. The bar is higher. You can revoke only if the non-conformity substantially impairs the value of the goods to you, and either you accepted expecting the seller would fix the problem (and they haven’t) or you didn’t discover the substitution because it was hard to detect or the seller’s assurances misled you.8Cornell Law Institute. Uniform Commercial Code 2-608 – Revocation of Acceptance in Whole or in Part A minor cosmetic difference probably won’t clear the “substantially impairs value” test; receiving industrial-grade components when you ordered medical-grade ones almost certainly will.
How to Reject Properly
If you catch the substitution quickly, rejection itself is straightforward but procedural. You must notify the seller within a reasonable time after delivery.9Cornell Law Institute. Uniform Commercial Code 2-602 – Manner and Effect of Rightful Rejection The UCC doesn’t name a specific number of days. What’s reasonable depends on the type of goods, how easily you can inspect them, and industry norms. For standard commercial products where a visual check reveals the wrong item, a few business days is the expectation. For complex equipment that needs testing, you’d have more time. The safe approach is to inspect and notify as quickly as you can.
Send the rejection notice in writing through a channel that creates a record: certified mail, email with a read receipt, or the supplier’s vendor portal. After rejecting, you must hold the goods with reasonable care long enough for the seller to arrange pickup.9Cornell Law Institute. Uniform Commercial Code 2-602 – Manner and Effect of Rightful Rejection You don’t have to ship them back at your own expense, but you can’t abandon them either.
Business buyers whose seller has no local agent nearby carry extra obligations. You must follow any reasonable instructions the seller gives about what to do with the rejected goods, as long as the seller covers your expenses. If the goods are perishable or losing value fast and the seller hasn’t given instructions, you have a duty to make reasonable efforts to sell them on the seller’s behalf. You’re entitled to reimbursement and a selling commission.10Cornell Law Institute. Uniform Commercial Code 2-603 – Merchant Buyer’s Duties as to Rightfully Rejected Goods Acting on these duties in good faith doesn’t count as accepting the goods.
The Supplier Can Sometimes Fix the Problem
Rejecting a shipment doesn’t always end things. The supplier may have a right to cure, under two circumstances.
If the contract deadline hasn’t passed yet, the supplier can notify you of the mistake and deliver conforming goods before the deadline runs out.11Cornell Law Institute. Uniform Commercial Code 2-508 – Cure by Seller of Improper Tender or Delivery; Replacement You can’t refuse a conforming delivery just because the first attempt was wrong, so long as the replacement is on time.
Even after the deadline has passed, a supplier who had reasonable grounds to believe the substitute would be acceptable gets additional time to deliver the correct item.11Cornell Law Institute. Uniform Commercial Code 2-508 – Cure by Seller of Improper Tender or Delivery; Replacement This comes up when the supplier shipped a newer model, an industry-standard equivalent, or an upgraded version. The supplier must notify you promptly that a conforming replacement is coming. Buyers get frustrated with this rule because a supplier who made a reasonable judgment call about what you’d accept gets a second chance even after blowing the deadline.
Recovering Your Money
Rejecting the wrong goods is only half the battle if you still need the original item. The UCC lets you “cover” by buying substitute goods from another source in good faith and without unreasonable delay. Your damages are the difference between what you paid for the replacement and the original contract price, plus incidental or consequential losses, minus any costs you saved because of the breach.
Cover isn’t mandatory. If you choose not to buy replacements, you can claim damages based on the market price of the goods at the time you learned of the breach minus the contract price. Either way, you can also recover incidental damages: the costs of inspecting, storing, and returning the rejected goods, plus commercially reasonable expenses tied to finding and buying replacements.12Cornell Law Institute. Uniform Commercial Code 2-715 – Buyer’s Incidental and Consequential Damages
Consequential damages go further. If the supplier knew at the time of contracting that you had particular needs, and the substitution caused losses you couldn’t reasonably prevent, those losses are recoverable too.12Cornell Law Institute. Uniform Commercial Code 2-715 – Buyer’s Incidental and Consequential Damages If the wrong part shuts down your production line and the supplier knew you were running on a tight schedule, the lost revenue from that downtime is on the table. The catch is that you must make reasonable efforts to minimize your losses. Sitting on your hands while damages pile up weakens the claim.
Risk of Loss Stays With the Supplier
When a supplier ships non-conforming goods, the risk of loss stays with the supplier until the problem is cured or you accept the delivery. If the substituted items are damaged in transit or destroyed while sitting in your warehouse awaiting return, that’s the supplier’s problem. If you revoke acceptance, you can treat the risk as having been on the supplier the whole time, to the extent your own insurance doesn’t cover the loss.13Cornell Law Institute. Uniform Commercial Code 2-510 – Effect of Breach on Risk of Loss Suppliers often miss this. Shipping the wrong item means carrying the financial risk on those goods throughout the entire dispute, even while they sit on your loading dock.
Documentation Protects Every Remedy
Good records make each of the above easier to pursue. Start with the basics: your original purchase order, the order confirmation from the supplier, and the packing slip or shipping manifest that arrived with the delivery. Line up item descriptions, model numbers, and SKUs across all three. The mismatch between what you ordered and what arrived is the core of any claim.
Photograph the delivered item and its packaging, including labels, serial numbers, and any product markings. If the substitution involves differences in materials, dimensions, or performance ratings, document those with measurements or spec sheets. Keep a written log noting the delivery date, the date you discovered the discrepancy, and the date you sent the rejection notice. So many of your rights depend on acting within a reasonable time that a clear chronology is often what separates a winning claim from a lost one.