A counterclaim is a claim which is brought against a plaintiff in a lawsuit by a defendant. For example, if a landlord sued a tenant for unpaid rent, the tenant might respond with a counterclaim which suggested that the landlord was actually in the legal wrong, thereby hoping to render his or her claim invalid. Counterclaims are typically filed as part of a defendant's answer to an original claim, and there is a specific style and format for counterclaims which must be followed for the court to accept them.

Essentially, a counterclaim raises issues which a defendant would have brought up in a court case, if he or she had been given the chance to go to court first. As such, counterclaims can contain a variety of material, ranging from accusations of fraudulent activity to claims which would pre-empt any attempt at a suit. The goal of a counterclaim is to turn the tables on the plaintiff by bringing up more issues in the case and demanding redress.

In a compulsory counterclaim, the defendant must file a counterclaim or remain silent on the issue. Not all counterclaims are compulsory, and the rules vary, depending on the region and the court. As a general rule, compulsory counterclaims involve only the original parties named in the suit, and they involve only the original situation which was brought to court. So, for example, a bank could sue a customer for unpaid fees, and the customer could respond with a counterclaim which stated that the bank had used illegal tactics to recover those fees.

In a permissive counterclaim, a defendant may raise issues in a counterclaim, but if he or she doesn't, the right to sue for redress at a future point remains. In the example above, if the defendant was planning on joining a class action lawsuit of bank customers who had been poorly treated, he or she would not be obliged to file a counterclaim, because the suit would include additional parties and the scope of the claim would be larger than the original suit.

When dealing with a lawsuit, it is a good idea to find out about the regional rules governing counterclaims, which is something a lawyer can help with. You don't want to miss out on filing a counterclaim and inadvertently waive your right to file suit in the future, and by the same token, you shouldn't feel hurried into filing a counterclaim if you can legally wait. Lawyers who specialize in such cases can give the best advice on what to do.