S.C. Code § 12-36-2560
On all sales of retailers liable for the tax imposed by Article 9 of this chapter (sales tax) made on an installment basis which conform to the provisions of the Uniform Commercial Code in which the retailer takes a security interest, the vendor may elect to include in the return only the portion of the sales price actually received by the retailer during the taxable period or to include the entire sales price in the return for the taxable period during which the sale was consummated. Having once elected either method of reporting the sales, the taxpayer must continue unless and until permission has been received from the department to make a change. Nothing in this section may be construed to permit delay in reporting sales under other terms of credit or cash sales.
The department may, for any cause, require a taxpayer to include in his returns the entire sales price of articles sold on an installment basis which conforms to the provisions of the Uniform Commercial Code in which the retailer takes a security interest.
S.C. Code § 12-36-2560