
    Mary-Catherine Carter, Respondent, v Guy T. Carter, Appellant.
    [697 NYS2d 127]
   —In a matrimonial action in which the parties were divorced by a judgment dated October 25, 1996, the defendant appeals from an order of the Supreme Court, Rockland County (Weiner, J.), dated April 6, 1999, which denied his motion, inter alia, to modify the judgment of divorce by directing that the defendant’s 40 IK plan be divided between the parties as of January 15, 1994, instead of January 3, 1994.

Ordered that the order is affirmed, with costs.

A separation agreement, which, as here, does not merge into thé judgment of divorce, survives as a separate contract to which the parties are bound (see, Riley v Riley, 179 AD2d 750; Lambert v Lambert, 142 AD2d 557). Consequently, while a judgment of divorce may be attacked pursuant to CPLR 5105, the underlying separation agreement will remain unimpeached unless challenged in a plenary action (see, Riley v Riley, supra; Culp v Culp, 117 AD2d 700). The failure of the defendant to commence a plenary action is fatal to his application. S. Miller, J. P., Thompson, Krausman, Florio and Schmidt, JJ., concur.  