Miss. Code Ann. § 27-15-171

If at any time any person liable for a tax under Sections 27-15-151 through 27-15-165 increases his classifications so as to require the payment of an additional tax, or shall begin business or construct or operate additional taxable units, application shall be made to the Tax Commission for additional privilege license, and upon the determination by the Tax Commission of the amount of tax due, shall pay the same. The Tax Commission shall issue such privilege license to expire on December 1 following, and shall collect the pro rata annual tax according to the number of months between the date of liability and December 1 following.