N.Y. CVP. LAW § 2104 : NY Code - Section 2104: Stipulations

An  agreement  between  parties  or  their
  attorneys relating to any matter in  an  action,  other  than  one  made
  between  counsel in open court, is not binding upon a party unless it is
  in a writing subscribed by him or his attorney or reduced to the form of
  an order and entered. With respect to  stipulations  of  settlement  and
  notwithstanding  the form of the stipulation of settlement, the terms of
  such stipulation shall be filed by the defendant with the county clerk.