N.Y. UCC Law § 2-209

Section 2--209. Modification, Rescission and Waiver.\n (1) An agreement modifying a contract within this Article needs no\nconsideration to be binding.\n (2) A signed agreement which excludes modification or rescission\nexcept by a signed writing or other signed record cannot be otherwise\nmodified or rescinded, but except as between merchants such a\nrequirement on a form supplied by the merchant must be separately signed\nby the other party.\n (3) The requirements of the statute of frauds section of this Article\n(Section 2--201) must be satisfied if the contract as modified is within\nits provisions.\n (4) Although an attempt at modification or rescission does not satisfy\nthe requirements of subsection (2) or (3) it can operate as a waiver.\n (5) A party who has made a waiver affecting an executory portion of\nthe contract may retract the waiver by reasonable notification received\nby the other party that strict performance will be required of any term\nwaived, unless the retraction would be unjust in view of a material\nchange of position in reliance on the waiver.\n