Except as provided in §80.274 of this title (relating to Motion for Rehearing Not Required in Certain Cases), in the absence of a timely motion for rehearing, a decision or order of the commission is final on the expiration of the period for filing a motion for rehearing. If a party files a motion for rehearing, a decision or order of the commission is final and appealable on the date of the order overruling the final motion for rehearing or on the date the motion is overruled by operation of law.