Miss. Code § 27-59-33
Each person to whom a Class II or Class III compressed gas user's decal is issued shall file an annual report with the commission. Such report shall be filed at a time designated by the commission, shall be on forms prescribed by the commission and shall contain such information as the commission deems reasonably necessary for the administration of this chapter.
The commission is authorized and empowered to promulgate rules and regulations setting forth the method for determining the quantity of compressed gas used on the highways of this state.
The portion of the privilege taxes prepaid at the time the application for the permit was made shall be deducted from the amount of tax shown to be due on the quantity of compressed gas used on the highways. Any balance due shall be paid to the commission at the same time the annual report is filed. If the amount prepaid exceeds the amount of tax shown to be due, a claim for refund or credit may be made. All such claims shall be supported by sufficient proof as to the extent of the claimant's tax liability on each motor vehicle. Refunds shall be made as provided in Section 27-55-19.
The operator of any motor vehicle or motor vehicles which are equipped so that more than one (1) type of fuel can be used shall be liable for the tax upon the total quantity of compressed gas consumed within the state, with no credit allowed for the purchase of any fuel other than compressed gas.
Miss. Code § 27-59-33