SDCL § 10-45-45: Records preserved by persons subject to tax--Inspection by department.

Every person subject to tax under this chapter shall keep records and books of all receipts and sales, together with invoices, bills of lading, copies of bills of sale, and other pertinent papers and documents. Such books and records and other papers and documents shall, at all times during business hours of the day, be subject to inspection by the secretary of revenue or his duly authorized agents and employees to determine the amount of tax due. Such books and records shall be preserved for a period of three years unless the secretary of revenue, in writing, authorized their destruction or disposal at an earlier date.