Miss. Code § 27-19-75
When any person has properly paid the privilege license in one (1) tax classification or gross weight bracket, or has become the owner of any vehicle after the payment of such privilege tax, and thereafter, because of an actual bona fide change of the use to which such vehicle is to be put, desires to increase the gross weight of such vehicle or to operate same in a different tax classification, the owner or operator thereof may increase the gross weight of such vehicle or change the tax classification thereof by making application therefor and surrendering the original privilege license issued upon such vehicle to the tax collector or commission and by paying the pro rata amount of the privilege tax in the new classification or gross weight bracket. Such owner or operator shall, however, be entitled to credit on such tax for the unexpired portion of the original license tax paid on such vehicle.
If any person shall operate his vehicle on the public highways in an improper classification or shall exceed the licensed gross weight of such vehicle, then such person shall be liable for the unexpired part of the annual tax in the tax classification and/or gross weight bracket in which he improperly or illegally operates, prorated from the first day of the month in which such illegal operation occurs until the expiration date of the license, plus a penalty thereon of twenty-five percent (25%). Provided, however, that such person shall be entitled to credit for the unexpired part of the annual tax paid by him on such vehicle, but the twenty-five percent (25%) penalty shall be computed before the allowance of such credit. No license shall be issued hereunder for less than the sum of Ten Dollars ($10.00) plus a penalty thereon of twenty-five percent (25%). No cash refund shall be given under this section and the credit herein provided for shall be applied only upon the replacement license issued.
Miss. Code § 27-19-75