S.C. Code § 12-37-1120
All property claimed to be "no situs" under this article shall be designated as being "in transit" upon the books and records of the warehouse wherein it is located, which books and records of the warehouse shall contain a full, true and correct inventory of all such property. The books and records of any such warehouse with reference to any such "in transit" property shall be at all times open to the inspection of all taxing authorities of this State and of any political subdivision thereof. Any person making claim to "no situs" status on any property as provided for by this article shall determine the percentage of amount of "no situs" property by dividing the total property shipped during the entire latest period located in South Carolina, not exceeding thirty-six months, into the total property shipped outside the State of South Carolina during the same period. The percentage determined in accordance with this section shall be applied to the inventory on hand on the last day of the accounting period of the person to determine the amount of "no situs" property.
Any person making claim to "no situs" status of any property under this article shall do so in the form and manner prescribed by the South Carolina Department of Revenue and all such claims shall be accompanied by a certification of the warehouseman as to the percentage used.
S.C. Code § 12-37-1120