Judgment, Supreme Court, New York County (Anil C. Singh, J.), entered January 4, 2013, awarding plaintiff landlord the principal sum of $115,138.78 in rent and tax escalation charges in connection with defendant tenant’s vacatur of the premises before the expiration of its lease, and bringing up for review an order, same court and Justice, entered November 15, 2012, which granted plaintiffs motion to amend the complaint and for summary judgment, unanimously affirmed, with costs. Appeal from the order, unanimously dismissed, without costs, as subsumed in the appeal from the judgment.
The parties’ lease required that any modification or discharge be in a writing signed by the party to be charged. The parties’ surrender agreement was not signed by the landlord and therefore had no binding effect. Further, the surrender agreement did not become binding upon the tenant’s mailing it to the landlord, as the “mailbox rule” for formation of contracts by dispatch of acceptance (see Buchbinder Tunick & Co. v Manhattan Natl. Life Ins. Co., 219 AD2d 463, 466 [1st Dept 1995]) was not implicated. The tenant’s claim of promissory estoppel based on the surrender agreement and the discussions leading up to it lacked merit because it had vacated the premises before signing the agreement, so the required element of detrimental reliance was lacking, and its evidence of the discussions did not show a clear and unambiguous promise (see generally MatlinPatterson ATA Holdings LLC v Federal Express Corp., 87 AD3d 836, 841-842 [1st Dept 2011]).
The court properly exercised its discretion in allowing amendment of the complaint to correct the alleged date of the tenant’s vacating the premises (see CPLR 3025 [b]), given that the corrected date conformed to an admission made by one of the tenant’s principals.
We have considered the tenant’s remaining contentions and find them unavailing. Concur—Mazzarelli, J.E, Saxe, Moskowitz and Manzanet-Daniels, JJ.