S.C. Code § 12-37-1610
The President or designated agent of every railroad company, whose track or roadbed, or any part thereof, is located in this State, shall annually, on or before the fifteenth day of the fourth month, following the close of the company's accounting period, file a return to the South Carolina Department of Revenue, under oath, on forms prescribed by the department. Such company shall also file a duplicate copy of the annual report to the Interstate Commerce Commission of the United States Government or a duplicate copy of the annual report required by the South Carolina Public Service Commission and any other report the Department of Revenue may require that shall accurately detail all real and personal property of the company within and without this State.
S.C. Code § 12-37-1610