In Kawarau Village Holdings v Ho Kok Sun  NZSC 150, the Supreme Court considered whether completion of all three-stages of a three-stage development was an essential term of a contract for the sale and purchase of apartments purchased off plans. The Supreme Court concluded that completion was an essential term. As the vendor was unable to complete the three-stages of development at the time of settlement, the purchasers of the apartments in the first stage were not obliged to settle their purchases.
The Supreme Court addressed the issue of essentiality in Mana Property Trustee v James Development, under which the courts assess essentiality by asking whether, unless the term in question was agreed at the time of contracting to be essential, the cancelling party would more probably than not have declined to enter into the contract. That question is determined objectively.
The minority in the Supreme Court suggested the majority had misstated the test set out in Mana Property. While the minority judgment considered that reference to the "centrality" of completion may be seen as a reference to its essentiality, that reference was followed by a statement that the purchasers were entitled to expect the vendor to live up to its promise relating to the development. That alludes to the existence of a promise, not the essentiality of the promise.
See the Court's decision here.