A counterclaim includes information about relief against an original claim that was filed by a plaintiff, explains Cornell University Law School. The person making the counterclaim is the defendant in the lawsuit, and the counterclaim includes information that directly refutes the original claim or information related to claims about actions that are not specifically related to the original claim. In these counterclaims, the defendant is in the offensive posture and bears the risk of proof.
A claim that directly refutes the original claim brought by the defendant is known as a compulsory counterclaim, says Cornell University Law School. Such a claim, if it is proven and accepted, nullifies the original claim, and it is known as compulsory because it cannot be brought up in a separate trial. An example of such a counterclaim is if the plaintiff sues the defendant for breach of contract, and the defendant offers information in the counterclaim that the contract was signed under fraudulent conditions. Other compulsory counterclaims are defined by how closely the action in question is connected to the original action.
Information in a permissive counterclaim does not have to be closely connected to the original action, according to Cornell University Law School. Such information does, however, need to be connected to some aspect of the legal relationship between both parties.