S.C. Code § 38-7-50
Every insurer insuring employers in this State against liability for personal injuries to their employees or death caused by the injuries, under the provisions of Title 42, shall pay a tax upon the premiums received whether in cash or notes in this State, or on account of business done in this State, for such insurance in this State at the rate of four and one-half percent of the amount of the premiums. For fiscal year 1990-91, the tax is at the rate of three and one-half percent of the amount of the premiums. For fiscal year 1991-92 and thereafter, the tax is at the rate of two and one-half percent of the amount of the premiums. This tax is in lieu of all other taxes on these premiums and must be assessed and collected as provided in this chapter. However, the insurers must be credited with all canceled or returned premiums actually refunded during the year on workers' compensation insurance including any unused premiums refunded or credited to policyholders as dividends.
If an insurer fails or refuses to make the return required by Section 38-7-60, the director or his designee shall assess the tax against the insurer at the rate provided for in this chapter on the amount of premiums he considers just and the proceedings thereon must be the same as if the return had been made.
S.C. Code § 38-7-50