86 N.Y.2d 685 (N.Y. 1995) (parallel cites: 660 N.E.2d 415; 636 N.Y.S.2d 734)
Oppenheimer & Co., Inc. v.
Whether the doctrine of substantial performance can satisfy an express condition precedent that required delivery of the prime landlord's written consent by a date certain, and, if not satisfied, whether the sublease was null and void such that the sublessee had no duty to perform.
Express conditions precedent—events that the parties explicitly make prerequisites to the formation or duty of performance, often signaled by language such as "if," "unless," "until," and "null and void unless"—must be literally performed; substantial performance of an express condition is insufficient. The nonoccurrence of an express condition prevents formation of the contract or the accrual of the duty it conditions, unless the condition is excused by waiver, estoppel, prevention, or a limited equitable doctrine avoiding disproportionate forfeiture when the condition is not a material part of the agreed exchange. Courts ascertain whether language creates an express condition by focusing on intent as expressed in the contract's words and structure.
The landlord's written consent was not delivered by the contractual deadline, so the express condition precedent failed. Substantial performance cannot cure failure of an express condition. No waiver, estoppel, prevention, or disproportionate forfeiture applied. The sublease was therefore null and void, and the sublessee had no contractual obligation to perform.
Oppenheimer is a cornerstone case on express conditions precedent. It teaches that courts will enforce clear conditional language as written, requiring literal compliance with both form and timing. For students, it sharpens the distinction between promises/constructive conditions (where substantial performance may soften breach) and express conditions (where it does not). The case also highlights recognized escape hatches—waiver, estoppel, prevention, and disproportionate forfeiture under the Restatement—while emphasizing their narrow application. Practically, Oppenheimer is a drafting lesson: if parties make a protection a condition with "null and void unless" and a date certain, courts will not substitute substantial performance or equitable gloss to rescue a missed condition.