- If the plaintiff owes you money, you can sue him or her. This is called a “counterclaim.”
o You can file a counterclaim even if the other side owes you money from a different dispute. Read the Rule: Maryland Rule 3-331(a) 
- If the is another defendant (someone else who the plaintiff sued in the same dispute) – and that defendant owes you money – you can file a “cross claim.”
- If there someone else who caused all or part of the harm but wasn’t sued by the plaintiff, you can “join” that party in the dispute.
Timing – You must file a counterclaim or cross claim within 10 days after the deadline to file the Notice of Intent to Defend. The Notice to Defend is due 15 days after you (a defendant) receive a copy of the Complaint.
Service – You must make sure that you serve (give court papers to) any new party. You must serve them with a copy of “all pleadings, scheduling notices, court orders, and other papers [that have been] previously filed in the action.” Do not personally give them a copy. For more information you can read Frequently Asked Questions About "Service of Process" in Maryland. 
Tip - If you choose any of these options, be clear and concise. Explain your story. This is not an opportunity to criticize the other side. It is not your chance to argue the whole case. Just include the highlights.
- To prepare for your case, use this Resource Guide  to walk through the same steps that you would have taken had you filed first.
- You cannot file for more money or other types of help (relief) than the District Court allows. If your claim is not right for District Court, your case can be transferred to Circuit Court.
- The original complaint and your counterclaim or crossclaim will both be heard during the same trial. But, if there is a good reason, the court can order that the trials be held at different times.