Yesawich, Jr., J. Appeal (transferred to this court by order of the Appellate Division, Second Department) from an order of the Supreme Court (Weiner, J.), entered April 7, 1989 in Rockland County, which, inter alia, denied defendant’s motion to annul a separation agreement contained in a stipulation of settlement.
Plaintiff’s 1987 divorce action was pending when in October 1988 she and defendant entered into a written stipulation purporting to settle the action. The "stipulation of settlement” contains all the indicia of a separation agreement, including a detailed schedule for distribution of the marital property. Moreover, it was signed and subscribed by the parties (see, Domestic Relations Law § 236 [B] [3]), and both they and their counsel variously referred to the agreement as such throughout the course of this litigation.
Apart from effecting the transfer of title to the family home to plaintiff, neither party otherwise followed the agreement’s mandate. Following considerable controversy between the parties regarding 1988 tax payments, defendant concluded that plaintiff’s refusal to abide by the terms of the agreement made it inoperable. Proceeding by order to show cause, defendant sought a hearing to determine the validity of the separation agreement; in his view the agreement was a nullity having been procured by fraud and "more importantly because of the total lack of implementation of the agreement” on plaintiff’s part. Plaintiff responded with her own order to show cause *649seeking essentially specific enforcement of the agreement. Supreme Court denied both motions and defendant appealed. We affirm.
A separation agreement is a contract; as such it cannot be annulled by motion (see, e.g., Lambert v Lambert, 142 AD2d 557, 558). The claim that the separation agreement is voidable must be made in a plenary action seeking such relief, or asserted as an affirmative defense or counterclaim (see, 2 Foster, Freed & Brandes, Law and the Family New York § 12:62, at 1017-1022 [2d ed]; Surlak v Surlak, 95 AD2d 371, 381, appeal dismissed 61 NY2d 906; see also, Christian v Christian, 42 NY2d 63, 72). As that has not occurred here, Supreme Court correctly denied defendant’s motion.
Order affirmed, without costs. Weiss, Mikoll and Yesawich, Jr., JJ., concur.