(a) Compulsory Counterclaims. A pleading shall state as a counterclaim any claim which at the time of serving the pleading the pleader has against any opposing party, if it arises out of the transaction or occurrence that is the subject matter of the opposing party's claim and does not require for its adjudication the presence of third parties of whom the court cannot acquire jurisdiction. But the pleader need not state the claim if (1) at the time the action was commenced the claim was the subject of another pending action, or (2) the opposing party brought the suit upon his claim by attachment or other process by which the court did not acquire jurisdiction to render a personal judgment on that claim, and the pleader is not stating any counterclaim under this Rule 13.
(b) Permissive Counterclaims. A pleading may state as a counterclaim any claim against an opposing party not arising out of the transaction or occurrence that is the subject matter of the opposing party's claim.
(c) Counterclaim Exceeding Opposing 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.
(d) Counterclaim Against the State. These rules shall not be construed to enlarge beyond the limits fixed by law the right to assert counterclaims or to claim credits against the State of South Carolina or an officer, agency, or governmental or political subdivision thereof.
(e) Counterclaim Maturing or Acquired After Pleading. A claim which either matured or was acquired by the pleader after serving his pleading may, with the permission of the court, be presented as a counterclaim by supplemental pleadings.
(f) Omitted Counterclaim. When a pleader fails to set up a counterclaim through oversight, inadvertence, or excusable neglect, or when justice requires, he may by leave of court set up the counterclaim by amendment.
(g) Cross-Claim Against Co-party. A pleading may state as a cross-claim any claim by one party 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. Such 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.
(h) Joinder of Additional Parties. Parties other than those to the original action may be made parties to a counterclaim or cross-claim in accordance with Rules 19 and 20.
(i) Separate Trials. Separate Judgments. If the court orders separate trials as provided in Rule 42(b), judgment on a counterclaim or cross-claim may be rendered in accordance with the terms of Rule 54(b) even if the claims of the opposing party have been dismissed or otherwise disposed of.
(j) Transfer. In an action brought in a court of limited jurisdiction, in the event the counterclaim or cross-claim tendered for filing is in excess of the jurisdictional amount or otherwise beyond the jurisdiction of said court, upon the payment of any fees required by statute, the action shall be transferred to the circuit court of the county to be there considered and tried as if the action had been there originally filed. If such counterclaim be a permissive counterclaim allowed under Rule 13(b), the transfer shall be in the discretion of the court in which the action is brought. If such permissive counterclaim is not transferred in the discretion of the court, the judgment in such action shall not be a bar to the claim if and when brought thereafter in another action.
Rules 13(a) through (i) are the same as the Federal Rules on counterclaims and cross-claims. These include and expand Code §§ 15-13-420, 15-15-30, 15-15-40, 15-15-50 and 15-15-70. Counterclaims arising out of the same transaction or occurrence that is the subject of the action are "compulsory" under Rule 13(a) and are barred by res judicata or estoppel by judgment if not asserted. All other counterclaims whether legal or equitable in nature are permissive, and may be pleaded against the opposing party. Separate trials on claims not directly related to the original action may be ordered by the court under Rule 13(i). Rule 13(j) is added to conform to State practice, in which there are courts of differing jurisdiction. This Rule 13 considerably broadens present State practice as to counterclaims, but will avoid much litigation and dispute whether the counterclaim or cross-claim is allowable under the old 1870 Code practice.