23 V.S.A. § 325

If the registration fee of the motor vehicle sought to be registered is less than the registration fee of the transferred motor vehicle, the Commissioner shall certify to the Commissioner of Finance and Management the facts pertinent to the difference of such registration fees, giving the name of the owner of such motor vehicle, his or her address, the amount of the original registration fee paid, the date of application for transfer, and the correct fee for the motor vehicle sought to be registered. The Commissioner of Finance and Management shall issue his or her warrant in favor of the owner for such percent of the difference in registration fees as the unexpired term bears to the entire registration period, but if a transfer of registration is made before the 15th day of any month, the transfer, for the purpose of the refund, shall be considered as having been made on the first day of such month. If such transfer of registration is made on or after the 15th day of any month, the transfer, for the purpose of the refund, shall be considered as having been made on the first day of the month following such application for transfer.