I would affirm the judgment appealed. “[W]hen parties set down their agreement in a clear, complete document, their writing should as a rule be enforced according to its terms. Evidence outside the four corners of the document as to what was really intended but unstated or misstated is generally inadmissible to add to or vary the writing” (W.W.W. Assoc. v Giancontieri, 77 NY2d 157, 162 [1990]). Here, the trial evidence established that the renewal lease was not entered into until May 14, 2002. The term of the lease is unambiguously set forth in the lease extension executed on that date and cannot properly be varied by resort to extrinsic evidence of the parties’ antecedent negotiations (see Chimart Assoc. v Paul, 66 NY2d 570, 572-573 [1986]).
Nor is the equitable remedy of reformation available to relieve *373plaintiff from the renewal terms that it drafted and to which it now objects. “[T]o overcome the heavy presumption that a deliberately prepared and executed written instrument manifested the true intention of the parties, evidence of a very high order is required” (George Backer Mgt. Corp. v Acme Quilting Co., 46 NY2d 211, 219 [1978]). Plaintiffs bare claim of unilateral mistake is unsupported by any showing, much less the requisite clear and convincing showing, that the mistake was attributable to fraud or any other conduct on defendant’s part (see Barclay Arms v Barclay Arms Assoc., 74 NY2d 644 [1989]; George Backer Mgt. Corp., 46 NY2d at 219-220; Nash v Kornblum, 12 NY2d 42, 47 [1962]).