; and (2) inserting after subsection (a) the following: (b) Refunds (1) In general At the conclusion of any hearing under this section in which refunds of amounts that have been paid are required, the Commission shall order the natural-gas company to make those refunds for the period beginning on the refund effective date established under paragraph (3) and ending on the date on which the new rate established by the Commission under subsection (a) takes effect in amounts in excess of those amounts that would have been paid under the just and reasonable rate, charge, classification, rule, regulation, practice, or contract that the Commission orders to be observed and in force. (2) Requirement The refunds required under paragraph (1) shall be made, with interest, to the persons who have paid the rates or charges that are the subject of the hearing. (3) Effective date (A) In general The Commission shall establish the refund effective date in accordance with this paragraph. (B) Hearings initiated on complaint In the case of a hearing initiated on a complaint, the refund effective date shall be— (i) not earlier than the date on which the complaint was filed; and (ii) not later than 150 days after that date. (C) Hearing initiated on motion of Commission In the case of a hearing initiated by the Commission on its own motion, the refund effective date shall be— (i) not earlier than the date on which the Commission publishes notice of the intent to initiate the hearing; and (ii) not later than 150 days after that date. (c) No final decision If the Commission has not rendered a final decision for a hearing under this section by the end of the 180-day period beginning on the date on which the hearing is initiated, the Commission shall state— (1) the reasons why the Commission has failed to render a decision