S.C. Code Ann. § 41-44-40
If the amount of the credit determined under Section 41-44-30(2) exceeds the credit allowed under Section 41-44-30 for that taxable year, then the taxpayer may carry the excess over to the immediately succeeding taxable years. However, the credit carryover may not be used for any taxable year that begins on or after ten years from the date of the qualified investment. The amount of the credit carryover from a taxable year must be reduced to the extent that the carryover is used by the taxpayer to obtain a credit under this chapter for any subsequent taxable year.