Wis. Stat. § 78.555
An excise tax of 6 cents per gallon is imposed on all general aviation fuel sold, used or distributed in this state except as otherwise provided in this chapter. The general aviation fuel tax is to be computed and paid as provided in this chapter. Except as otherwise provided in this chapter, the general aviation fuel licensee, shall collect from the purchaser and the purchaser shall pay to the licensee the tax imposed by this section on each sale of general aviation fuel by the licensee at the time of the sale, irrespective of whether the sale is for cash or on credit. In each subsequent sale or distribution of general aviation fuel on which the tax has been collected as provided in this subsection, the tax collected shall be added to the selling price so that the tax is paid ultimately by the user of the general aviation fuel.
Wis. Stat. § 78.555