S.C. Code § 5-5-20
After the date of official council action if a petition executed by fifteen percent of the qualified electors is presented to the municipal governing body, certified by the county election commission, for an election to determine or change the form of government or if the municipal governing body shall by ordinance call for such an election, the municipal governing body shall conduct a special election not later than ninety days nor earlier than thirty days after the receipt of the certified petition or the passage of the council ordinance; provided, however, that no referendum shall be held pursuant to ordinance of the municipal council sooner than two years following the date the form of municipal government is initially selected pursuant to the provisions of this chapter.
S.C. Code § 5-5-20