Georgia Code Title 15. Courts § 15-10-45

(a) If any defendant has a counterclaim against the plaintiff arising out of the transaction or occurrence that is the subject matter of the plaintiff's claim, which counterclaim does not require for its adjudication the presence of third parties over whom the court cannot obtain jurisdiction, such counterclaim shall be asserted by the defendant at or before the hearing on the plaintiff's claim or thereafter be barred.

(b) If any defendant has a counterclaim against the plaintiff other than a compulsory counterclaim described in subsection (a) of this Code section, such counterclaim may be asserted by the defendant at or before the hearing on the plaintiff's claim.

(c) If any defendant asserts a counterclaim against the plaintiff, the defendant shall file with the court a statement of the counterclaim in concise form and free from technicalities. The defendant's counterclaim shall give the plaintiff reasonable notice of the basis for each claim contained in the counterclaim. The defendant shall sign the counterclaim. At the request of a defendant, the judge or clerk may prepare the counterclaim. Verification of a counterclaim shall not be required.

(d) If the amount of a counterclaim exceeds the jurisdictional limits of the magistrate court, the case shall be transferred to any court of the county which has jurisdictional limits which exceed the amount of the counterclaim. If there is more than one court to which the action may be transferred, the parties may agree on the court to which the action shall be transferred, and, in the absence of any agreement, the judge of the magistrate court shall determine the court to which the action shall be transferred. If there is no other court to which the action may be transferred, it shall be transferred to the superior court of the county.

(e) A counterclaim may in the discretion of the magistrate be tried either separately or jointly with the plaintiff's claim.