S.C. Code Ann. § 7-15-670: Declaration by covered voter.

(A) A covered voter may use the declaration accompanying a federal write-in absentee ballot as an application for a military-overseas ballot simultaneously with the submission of the federal write-in absentee ballot, if the declaration is received by the appropriate election official by seven o'clock p.m. on election day.

(B) To receive the benefits of this article, a covered voter must inform the appropriate election official that the voter is a covered voter. Methods of informing the appropriate election official that a voter is a covered voter include:

(1) the use of a federal postcard application or federal write-in absentee ballot;

(2) the use of an overseas address on an approved voter registration application or ballot application; and

(3) the inclusion on an approved voter registration application or ballot application of other information sufficient to identify the voter as a covered voter.