If a dealer fails to file any statement required by section 3.475, the tax administrator shall proceed forthwith to determine from as many available sources as the tax administrator determines reasonable the amount of motor vehicle fuel sold distributed or used by such dealer for the period unreported, and such determination shall in any proceeding be prima facie evidence of the amount of fuel sold, distributed or used. The tax administrator shall immediately assess the dealer for the license tax upon the amount determined, adding thereto a penalty of 10 percent of the tax. The penalty shall be cumulative to other penalties provided in this code.