S.C. Code Ann. § 12-8-1010: Withholding exemptions and exemption certificates.

(A)(1) Every employee shall furnish the employer with a signed withholding exemption certificate on or before the date employment begins indicating the number of withholding exemptions which the employee claims. A properly completed federal withholding exemption certificate is acceptable for South Carolina purposes.

(2) The number of exemptions claimed for South Carolina may not exceed the lesser of the number allowed under Internal Revenue Code Section 3402 or the number actually claimed for federal income tax withholding purposes. If an employee claims fewer exemptions for South Carolina than for federal purposes, the employee shall furnish the employer with a federal withholding exemption certificate which indicates that it is for state purposes.

(B) A withholding exemption certificate is effective upon the first payment of wages after the certificate is furnished to the employer and continues in effect until a new certificate is furnished to the employer.

(C) If an employee fails to furnish an employer with an exemption certificate as provided by this chapter, the number of withholding exemptions claimed is zero.