S.C. Code Ann. § 56-1-90
The Department of Motor Vehicles may require every applicant to submit for identification purposes proof of name, Social Security number, and date and place of birth when applying for a driver's license. An applicant for a driver's license, driver's permit, or special identification card or a renewal thereof may sufficiently prove the existence and validity of his Social Security number, for purposes of Section 14-7-130, by any reasonably reliable document containing the Social Security number. Such a document includes, but is not limited to, an official Social Security card, Social Security check, Social Security form SSA-1099, letter from the Social Security Administration, voter registration card, payroll stub, Federal W-2 form, or U.S. military identification card. The numbers may also be obtained from the Department of Revenue pursuant to Section 12-54-240(B)(7) which permits the Department of Revenue to submit taxpayer Social Security numbers to the Department of Motor Vehicles and to the State Election Commission.
For purposes of this section, when a licensee is applying for a replacement license, the Department of Motor Vehicles must accept an affidavit as evidence that the licensee has established the existence and validity of his Social Security number at the time of the original license application. The driver's license number of a person may be his Social Security number.
This section does not prevent issuance of a driver's license or identification card to a foreign exchange student participating in a valid foreign exchange program.