Voters are not required to show ID when they register on paper form (NOTE: is this still true?), but they will need to present a photo identification card when they go to the poll to vote in person. To get an ID, citizens must show proof of identity, usually a birth certificate or citizenship papers). Here are the forms of ID that are acceptable:
SC Driver’s License
SC Department of Motor Vehicles ID Card (anyone can get this at the same office where people get a driver's license)
includes SC Concealed Weapons Permit
SC Voter Registration Card with Photo (voters can get this at the county voting office)
US Passport
Federal Military ID
includes all Department of Defense Photo IDs and the Department of Veterans Affairs Benefits Card