S.C. Code Ann. § 12-6-2252 — Allocation and apportionment of business income

(A) A taxpayer whose principal business in this State is (i) manufacturing or a form of collecting, buying, assembling, or processing goods and materials within this State, or (ii) selling, distributing, or dealing in tangible personal property within this State, shall make returns and pay annually an income tax that includes its income apportioned to this State. Its income apportioned to this State is determined by multiplying the net income remaining after allocation pursuant to Sections 12-6-2220 and 12-6-2230 by the sales factor defined in Section 12-6-2280.
(B) If a sales factor does not exist, the remaining net income is apportioned to the business's principal place of business.