35 Miss. Code R. § 4-10-01-901
Purchases by contractors and subcontractors of work equipment, tools, building forms, repair parts for work equipment and similar items of tangible personal property that do not become component parts of the structure being erected are taxed at the regular retail rate of sales or use tax and any applicable special tax. When property of this type has been previously used in another state and is imported into this State for use, the use tax is due on the fair market value of the property at the time of importation. At no time shall the value be less than 20% of original cost. Credit for sales or use tax paid to another state in which the property was acquired or used may be taken in computing the amount of use tax due this State. The credit must be computed by applying the rate of sales or use tax paid to another state to the value of the property at the time it enters Mississippi.
35 Miss. Code. R. § 4-10-01-901