This case arises out of the refusal of Richard Alexander, in his capacity as the Clerk for the State Court of Gwinnett County, to file a motion to compel discovery under a particular case number requested by the filing party, Thomas Gibson. The requested case number had previously been assigned to a case to which the motion to compel was directly related, and Gibson filed a petition for a writ of mandamus in an effort to force Alexander to file the motion to compel under this case number. The trial court granted the mandamus petition, and Alexander appeals from this ruling. Because we find that Alexander had a clear duty as the Clerk of the court to file the motion to compel under the requested case number without making an independent determination about whether a new case number should be assigned, we affirm.
*395By way of background, on May 8, 2014, Gibson filed a complaint in Gwinnett County State Court against Samuel Wright, and the case was assigned Case No. 14-C-020432-2. When Wright failed to answer, a default judgment was entered against him on December 2, 2014. Gibson served post-judgment interrogatories on Wright on January 13, 2015, but again, Wright failed to respond. Gibson then prepared a motion to compel discovery, using Case No. 14-C-020432-2, which he presented for filing in Gwinnett County State Court on July 17, 2015. However, a representative of the Clerk’s office indicated to Gibson that the motion to compel would have to be filed under a new case number, 15-C-03773-2, because the motion was being filed more than thirty days after the default judgment had been entered against Wright. Despite Gibson’s repeated efforts to file the motion to compel under Case No. 14-C-020432-2, he was forced to proceed under Case No. 15-C-03773-2.
“Mandamus will issue against a public official only where the petitioner has demonstrated a clear legal right to relief or a gross abuse of discretion.” Gwinnett County v. Ehler Enterprises, 270 Ga. 570 (1) (512 SE2d 239) (1999).
The duty which a mandamus complainant seeks to have enforced must be a duty arising by law, either expressly or by necessary implication; and the law must not only authorize the act be done, but must require its performance.
(Punctuation and footnote omitted.) Gilmer County v. City of East Ellijay, 272 Ga. 774, 776 (1) (533 SE2d 715) (2000).
In this regard, state court clerks have the legal duty “to file pleadings, not to ascertain their legal effect.” (Citation omitted.) Ford v. Hanna, 292 Ga. 500, 501 n. 2 (739 SE2d 309) (2013). These “duties of the clerk relating to the filing of pleadings are ministerial in nature” and do not involve the exercise of discretion. Hood v. State, 282 Ga. 462, 464 (651 SE2d 88) (2007). Here, instead of simply executing his ministerial duty of filing the motion to compel discovery under the case number of the matter to which the motion was related, Alexander and members of his office apparently made the decision to assign the motion a new case number based on the office’s interpretation of OCGA § 15-6-77 (e) (1). That statute states in relevant part with respect to “[cjosts in civil cases . . . [that] [a]ny postjudgment proceeding filed more than 30 days after judgment or dismissal in an action shall be considered as a new case for the purposes of this Code section.” (Emphasis supplied.) In other words, “postjudgment proceedings filed more than 30 days after judgment . . . shall be considered a new case for purposes of calculating the costs the *396superior court clerk is entitled to charge and collect.” (Emphasis supplied.) McFarland & Assocs., P.C. v. Hewatt, 242 Ga. App. 454 (529 SE2d 902) (2000).
Notably, OCGA § 15-6-77 (e) (1) does not deal with the assignment of case numbers, but the calculation of costs for postjudgment motions filed more than thirty days after a judgment is entered. See id. Indeed, Alexander has cited to no authority to show that he was legally required to file Gibson’s motion to compel under a new case number. What Alexander was legally required to do, however, was file the motion to compel upon collecting appropriate costs as calculated per OCGA § 15-6-77 (e) (1), but without attempting to determine whether the document should legally be filed under the previously assigned case number of Gibson’s original complaint. The propriety of the filing should be considered, if at all, by the court upon motion by the parties or on its own motion, and not by the Clerk.1
Because Gibson had a clear legal right to compel Alexander to fulfill his ministerial duty of filing Gibson’s motion to compel discovery under Case No. 14-C-020432-2 here, we uphold the trial court’s decision to grant Gibson’s petition for a writ of mandamus.
Judgment affirmed.
All the Justices concur, except Thompson, C. J., and Hines, P. J., who dissent.The dissent’s citation to Brown v. King, 266 Ga. 890 (472 SE2d 65) (1996) and Uniform Superior Court Rule (“USCR”) 39.2 for the proposition that the Clerk was authorized to assign a new case number to the motion to compel discovery here is inapposite. Brown specifically deals with contempt actions to enforce court-ordered child support payments, which are “independent proceeding[s] that [are] ancillary to the divorce action” and maybe assigned anew case number under USCR 39.2. Id. at 891 (1), (2). The instant case does not involve a contempt action.