S.C. Code § 7-5-150
The registration books shall be closed thirty days before each election, but only as to that election or any second race or runoff resulting from that election, and shall remain closed until the election has taken place, anything in this article to the contrary notwithstanding; provided, that the registration books shall be closed thirty days before the June primary and shall remain closed until after the second primary and shall likewise be closed thirty days before the November general election. They shall thereafter be opened from time to time in accordance with the provisions of this article. Any person eligible to register who has been discharged or separated from his service in the Armed Forces of the United States, and returned home too late to register at the time when registration is required, is entitled to register for the purpose of voting in the next ensuing election after the discharge or separation from service, up to 5:00 p.m. on the day of the election. This application for registration must be made at the office of the board of voter registration and elections in the county in which the person wishes to register, and if qualified, the person must be issued a registration notification stating the precinct in which he is entitled to vote and a certification to the managers of the precinct that he is entitled to vote and should be placed on the registration rolls of the precinct. Persons who become of age during this period of thirty days shall be entitled to register before the closing of the books if otherwise qualified.
S.C. Code § 7-5-150