S.C. Code Ann. § 12-6-5020
(A) A consolidated return may be filed for the following corporations:
(2) two or more corporations under substantially the entire control of the same interest.
The terms "substantially controlled" and "substantially the entire control" mean the ownership of at least eighty percent of the total combined voting power of all classes of stock of all corporations that are a party to a consolidated return.
(D) A consolidated return means a single return for two or more corporations in which income or loss is separately determined as follows: