Ark. Code Ann. § 23-4-416

In the event that the amount of refunds ordered by the Arkansas Public Service Commission in its final order is subsequently determined to have been excessive, either on rehearing or in accordance with a court decision on judicial review, the public utility subject to the order shall be entitled to impose an additional surcharge on the affected customers to recover that portion of the refunds to which it was entitled, together with interest as determined by the commission at a rate not to exceed the maximum interest rate otherwise allowed by law. The surcharge shall be assessed over a period equal to the period between the date the rates were implemented under bond and the date of the commission's final order. The surcharge shall be distributed among the affected customers in proportion to the amount of refunds those customers received.