S.C. Code Ann. § 33-5-103: Resignation of registered agent.

(a) A registered agent may resign his agency appointment by signing and delivering to the Secretary of State for filing the signed original and two exact or conformed copies of a statement of resignation. The statement may include a statement that the registered office is also discontinued.

(b) After filing the statement the Secretary of State shall mail one copy to the registered office (if not discontinued) and the other copy to the corporation at its principal office.

(c) The agency appointment is terminated, and the registered office discontinued if so provided, on the thirty-first day after the date on which the statement was filed.