1. Deprivation of expected benefit: The more the non-breaching party is deprived of the benefit which he reasonably expected, the more likely it is that the breach was material.

2. Part performance: The greater the part of the performance which has been rendered, the less likely it is that a breach will be deemed material. Thus a breach occurring at the very beginning of the contract is more likely to be deemed material than the same "size" breach coming near the end.

3. Likeliness of cure: If the breaching party seems likely to be able and willing to cure, the breach is less likely to be material than where cure seems impossible.

4. Willfulness: A willful (i.e., intentional) breach is more likely to be regarded as material than a breach caused by negligence or other factors.

5. Delay: A delay, even a substantial one, will not necessarily constitute a lack of substantial performance. The presumption is that time is not "of the essence" unless the contract so states, or other circumstances make the need for promptness apparent. (Even if the contract does contain a "time is of the essence" clause, a short delay will not be deemed "material" unless the circumstances show that the delay seriously damaged the other party.)

1. "Perfect tender" rule: UCC §2-601 says that as long as the contract does not involve installments (i.e., multiple deliveries), "Unless otherwise agreed…if the goods or tender of delivery fail in any respect to conform to the contract, the buyer may (a) reject the whole; or (b) accept the whole; or (c) accept any commercial unit or units and reject the rest." On its face, this section seems to impose the "perfect tender" rule — that is, it seems to give the buyer the right to cancel the contract, and refuse to pay, if the goods deviate from the contract terms in any respect, no matter how slight.

2. Mechanics of rejection: The buyer may "reject" any non-conforming delivery from the seller. As noted, in theory this right exists if the goods deviate in any respect from what is required under the contract. But the buyer's right of rejection is subject to some fairly strict procedural rules:

3. Revocation of acceptance: Even if the buyer has "accepted" the goods, if he then discovers a defect he may be able to revoke his acceptance. If he revokes, the result is the same as if he had never accepted — he can throw the goods back on the seller and refuse to pay.

4. Cure: Both the buyer's right to reject and his right to revoke an acceptance are subject to the seller's right to cure the non-conformity. See §2-508(1).

5. Installment contracts: The Code is more lenient to sellers under installment contracts (i.e., contracts calling for several deliveries) than in single delivery contracts. In the case of an installment contract, "the buyer may reject any installment which is non-conforming if the non-conformity substantially impairs the value of that installment and cannot be cured.…" §2-612(2). So a slight non-conformity in one installment does not allow the buyer to reject it, as he could in a single-delivery contract.

1. Implied promise of cooperation: Courts sometimes express this concept by saying that each party makes the other an "implied promise of cooperation." One consequence of a breach of this implied promise is that the non-occurrence of the condition to that party's duty is excused. (Example: P agrees to live with D, his grandmother, and to care for her for the rest of her life, in return for D's promise to leave P $100,000 in D's will. P lives with D for seven years, at the end of which D unreasonably forces P to leave the house. Five years later, D dies. P will be able to recover the $100,000, even though he did not live with D for the rest of her life. The reason is that the non-occurrence of the condition — caring for D for the rest of her life — was excused by D's failure to cooperate.)

1. Minor conditions: Generally, the court is much more likely to find that the condition is waived if it is a minor one, such as a procedural or technical one.

2. Continuation of performance: If a promisor continues his own performance after learning that a condition of duty has failed to occur, his conduct is likely to be found to operate as a waiver of the condition. (Example: Insurer insures Owner's house for fire; Insurer's duty to pay a claim is expressly conditional upon notice by Owner within seven days of any fire. Owner gives notice three weeks after a fire. Insurer sends an adjuster, attempts to make a settlement, and otherwise behaves as if it is not insisting on strict compliance with the notice provision. This continuation of performance will probably be found to be a waiver of the timely-notice condition.)