Rule 1.241 Compulsory counterclaims

If someone sues you and you have a related claim against them, you have to bring it up in that same lawsuit. This is called a compulsory counterclaim. It applies when your claim is already fully formed (not something that hasn't happened yet), it isn't already part of another lawsuit, and it comes from the same event or situation that the original lawsuit is about.

If you skip this step and don't raise your claim during the case, you usually lose your chance to bring it up later. Once the court reaches a final decision in the case, that decision blocks you from filing a separate lawsuit later based on that same related claim, even if you never mentioned it the first time.

There is one exception. You don't have to bring your counterclaim in the same case if doing so would require adding someone else to the lawsuit who is necessary for deciding that claim, but who the court has no legal power to bring into the case. In that situation, you can still raise your claim later, in a separate case.