Maryland Rules of Civil Procedure|Rule 2-331 - Counterclaim and Cross-Claim

                                                
(a) Counterclaim Against Opposing Party. A party may assert as a counterclaim any claim that party has against any opposing party, whether or not arising out of the transaction or occurrence that is the subject matter of the opposing party's claim. A counterclaim may or may not diminish or defeat the recovery sought by the opposing party. It may claim relief exceeding in amount or different in kind from that sought in the pleading of the opposing party.
(b) Cross-Claim Against Co-Party. A party may assert as a cross-claim any claim that party has against a co-party arising out of the transaction or occurrence that is the subject matter either of the original action or of a counterclaim therein or relating to any property that is the subject matter of the original action. The cross-claim may include a claim that the party against whom it is asserted is or may be liable to the cross-claimant for all or part of a claim asserted in the action against the cross-claimant.
(c) Joinder of Additional Parties. A person not a party to the action may be made a party to a counterclaim or cross-claim and shall be served as a defendant in an original action. When served with process, the person being added shall also be served with a copy of all pleadings, scheduling notices, court orders, and other papers previously filed in the action.
(d) Time for Filing. If a party files a counterclaim or cross-claim more than 30 days after the time for filing that party's answer, any other party may object to the late filing by a motion to strike filed within 15 days of service of the counterclaim or cross-claim. When a motion to strike is filed, the time for responding to the counterclaim or cross-claim is extended without special order to 15 days after entry of the court's order on the motion. The court shall grant the motion to strike unless there is a showing that the delay does not prejudice other parties to the action.
Md. R. Civ. P. Cir. Ct. 2-331
 This Rule is derived as follows:
Section (a) is derived from former Rule 314 a 1 and 2.
Section (b) is derived from former Rule 314 b.
Section (c) is derived from former Rule 314 c and d 3.
Section (d) is derived from former Rule 314 d 2.
Adopted April 6, 1984, eff. July 1, 1984. Amended April 7, 1986, eff. July 1, 1986; June 21, 1995, eff. Sept. 1, 1995; June 7, 2011, eff. July 1, 2011.