Performance of a sales contract is controlled by the agreement between the seller and the buyer. If identified goods are destroyed through no fault of either party, and risk has not passed to the buyer, the parties are excused from performance. Payment is always due at the time of delivery. A buyer or lessee can always reject delivered goods on discovery of a defect, regardless of previous opportunities to inspect. If a buyer or lessee is in breach, the seller or lessor can cancel the contract and sue for damages. If a seller or lessor cancels a contract without justification, he or she is in breach, and the buyer or lessee can sue for damages. A buyer's principal obligation is to tender delivery. In an installment contract, a buyer can reject any installment for any reason. A seller or lessor cannot consider a buyer or lessee in breach until the time for performance has past