S.C. Code Ann. § 12-6-5030
(B)
(1) A composite return is a single return for two or more taxpayers having the same tax year in which each participant's share of the partnerships or "S" Corporation's taxable income or loss is separately computed and added together to arrive at the total tax due on the composite return. The partnership or "S" Corporation may elect to determine each participant's tax due by one of the following methods:
(C)