When a seller fails to deliver or delivers nonconforming goods the buyer rightfully rejects, the buyer does not have to sit and wait for a lawsuit to work out its damages. UCC 2-712 lets the buyer go into the market, buy reasonable substitute goods, and then recover the difference between what it paid to cover and the original contract price, plus incidental and consequential damages, minus any expenses the buyer saved as a result of the seller's breach.

Cover is optional, not mandatory -- a buyer's failure to cover does not itself bar recovery. But a buyer who does not cover is generally limited to the market-price measure in UCC 2-713 instead, which prices the loss as of when the buyer learned of the breach and is often more speculative and harder to prove than an actual, documented substitute purchase.

To recover under 2-712, the buyer's substitute purchase must be made in good faith, without unreasonable delay, and must be a reasonable purchase of goods in substitution for those due from the seller. The substitute goods need not be identical to the contract goods, only commercially reasonable substitutes under the circumstances.

UCC 2-713 supplies the fallback measure -- contract price versus market price at the time the buyer learned of the breach -- for a buyer who does not cover, or whose cover is later found improper. Cover is generally the more favorable position for a buyer because it substitutes an actual, documented transaction price for a contested, retrospective market-price estimate that both sides can dispute with competing evidence.

A buyer proves cover with the substitute purchase records, a timeline showing the purchase followed promptly after the breach, and evidence the substitute goods were a reasonable stand-in. A seller attacking the claim argues the substitute purchase was unreasonable -- too expensive, not truly comparable, delayed without justification, or made in bad faith -- and may also argue the buyer failed to deduct expenses genuinely saved by not having to perform under the original contract.

Because cover fixes an actual number rather than a contested market estimate, it tends to compress the damages fight down to the reasonableness of the substitute purchase itself. Juricratic models cover and the market-price measure as two alternate damages paths off the same breach node, with a reasonableness-and-timeliness dial on the cover path; comparing the two paths side by side lets a user see how much the choice of measure moves the modeled recovery range, without asserting either figure as a predicted award.