§ 18-c. Refunds by the commission. Whenever it appears that any person, firm, corporation or municipal corporation, has paid to the commission fees or other charges in excess of the amount legally chargeable against such person, firm, corporation or municipal corporation, the commission shall have power, within three years after the date of such payment, to refund to such person, firm, corporation or municipal corporation the amount of such excess. Such refund may be made upon audit by the comptroller, from any moneys in the hands of the commission, not as yet turned over to the department of taxation and finance.