S.C. Code § 58-27-2090
When, in the judgment of the commission, there is a reasonably substantial affiliation of any electrical utility engaged in business in this State with any other corporation or person or when, in the judgment of the commission, any other corporation or person either exercises or is in position to exercise, by reason of ownership or control of securities or for any other cause, any reasonably substantial control over the business or policies of any electrical utility engaged in business in this State, the burden of proof shall be upon the electrical utility to establish as determined by the commission the reasonableness, fairness, and absence of injurious effect upon the public interest of any fees or charges growing out of any transactions between any electrical utility and such other corporation or person (a) in relation to supervision, management, construction, or engineering, services or contract, (b) for the sale of material, supplies, equipment, or other commodities, or (c) for any other purpose. Every electrical utility shall be required to produce, if so ordered by the commission in a pending proceeding, for the information of the commission and the other parties all such contracts, papers, and documents relating thereto and explanatory thereof as may be required by the commission, and unless the reasonableness, fairness, and absence of injurious effect upon the public interest of such fees and charges are established as determined by the commission, the same shall not be allowed by the commission for rate-making purposes.
The commission shall not allow for rate-making purposes any fees or expenses included in any contract or agreement with an affiliate representing charges that the commission has directly disallowed in its rate-making orders.
S.C. Code § 58-27-2090