If you have been sued and have claims against the plaintiff, you may be able to sue the plaintiff by asserting a counterclaim in the action. A counterclaim is initiated when the pleading containing it is served. CPLR 203(d).  It is typically contained in a defendant’s answer to a complaint.

Counterclaims are subject to the same statute of limitations as regular claims, however, if the time has expired but the counterclaim was not time-barred at the time the original complaint was filed, it may be asserted during the action if the counterclaim arises out of the same facts and circumstances alleged in the complaint. Such counterclaims can be pursued only to the extent of the demand within the complaint. CPLR 203(d).  A counterclaim in an amended pleading is treated as though presented in the original pleading for statute of limitations purposes. CPLR 203(f).

A counterclaim may assert any claims against the plaintiff, regardless of whether those claims are related to the subject matter of the action. CPLR 3019(b).

Where a counterclaim raises claims against a person not yet party to the action, he or she must be served with a summons and answer containing the counterclaim, whereupon he or she becomes a party to the action. CPLR 3019(d).

The time in which a counterclaim may be asserted is computed from the time when the underlying facts and circumstances became known or reasonably should have become known. CPLR 203(g).

A reply to a counterclaim must be served within twenty (20) days of service of the pleading containing the counterclaim. CPLR 3011.

Any counterclaim may be asserted in a responsive pleading or a separate action. In federal practice, some counterclaims are compulsory under Rule 13 of the Federal Rules of Civil Procedure.

A counterclaim may be asserted by a third party defendant. CPLR 1008.