In addition to responding to each allegation in a complaint, an answer might also include counterclaims. When a defendant raises a counterclaim against a plaintiff, the defendant is essentially starting a lawsuit against the plaintiff. The counterclaim does not have to be related to the plaintiff’s claim or claims. The defendant includes a counterclaim in the answer by essentially including complaint-like allegations in the body of the answer. Even when the answer includes a counterclaim, the answer need only be mailed to the plaintiff.
If an answer includes a counterclaim, the plaintiff must answer the counterclaim by preparing, and serving and filing a document called a reply. The format of a reply is much like the format of an answer. The plaintiff may include affirmative defenses, additional counterclaims and third-party claims. A reply is served on the defendant and filed like an answer, that is, usually by mail..