35 Miss. Code R. § 4-05-05-402
Income received from the temporary storage of fuel or other fuel products in this state pending shipping or mailing of the property outside this state is exempt from tax. The exemption is available whether or not the final determination of the property's destination can be made prior to storage. It is the responsibility of the owner of the fuel terminal to obtain a signed Affidavit of Temporary Storage from each customer annually. The Affidavit is completed by the customer to indicate what percentage of goods will be shipped out of state. The percentage should be based on prior year's shipments, however, a reasonable estimate may be used if there is an absence of prior year information. Any Affidavit accepted in good faith will be accepted as satisfactory documentation of exempt sales. Sales tax is due on any goods to be shipped within this state. The storage and handling of natural gas in underground salt domes, caverns, or other underground structures are exempt.
35 Miss. Code. R. § 4-05-05-402