S.C. Code Ann. § 7-15-660: Voting precinct assignment.

An overseas voter who is registering to vote, and who is eligible to vote in this State shall use, and must be assigned to, the voting precinct of the address of the voter's last place of residence in this State, or in the case of a voter described by Section 7-15-610(5)(e), the address of the voter's parent's or legal guardian's place of last residence in this State. If that address is no longer a recognized residential address, the overseas voter must be assigned an address within the voting precinct of the last place of residence for voting purposes.