S.C. Code Ann. § 12-6-5000 — Filing of separate or joint federal returns by husband and wife; same status required on state return; nonresidents; where no federal return filed

(A) If the federal taxable income of a husband and wife are determined on separate federal returns, their South Carolina taxable income must be separately reported and taxed.
(B) If both a husband and wife are residents, and if their federal taxable income is determined on a joint federal return, their South Carolina taxable income must be reported and taxed on the basis of a joint South Carolina income tax return.
(C)(1) If both husband and wife are nonresidents or if the husband or wife is a resident and the other is a nonresident, and if their federal taxable income is determined on a joint federal return, their South Carolina taxable income must be reported and taxed on the basis of a joint South Carolina income tax return except as provided in subitem (2).
(2) If a nonresident taxpayer is a resident of a state which does not allow a resident of South Carolina to file a joint return with a spouse, the nonresident taxpayer shall file a separate South Carolina income tax return from the spouse. The nonresident taxpayer shall calculate taxable income on a federal return as a married person filing separately to determine how the separate federal taxable income is calculated.
(D) If neither a husband nor wife files a federal return, their South Carolina taxable income must be determined on a separate basis unless both elect to have their South Carolina taxable income determined on a joint basis by filing a joint South Carolina tax return.