An adversary proceeding in bankruptcy is a lawsuit filed within the debtor’s bankruptcy case. Any party can file an adversary proceeding in a bankruptcy — the trustee, a creditor, or the debtor. The purpose of an adversary proceeding is to obtain some form of relief that requires a judge’s attention and cannot be accomplished through the routine bankruptcy case itself.
An adversary proceeding starts when the person who is suing (the plaintiff) files a complaint with the bankruptcy court. Once the defendant is served with the complaint, s/he has a certain number of days to respond,. To respond, the defendant must file a written answer. If the defendant does not file an answer on or before the deadline, the court will enter a default, and the plaintiff can obtain a default judgment. Otherwise the adversary case will be decided on the merits by trial or dispositive motion.