Has the undyed diesel tax rate increased? Yes. Beginning July 1, 2017, the undyed diesel tax rate is increased to 21 cents. See important notice 17-08 for rate increases for subsequent years. December 11, 2017 15:45 Related articles I am a wholesaler with gasoline and/or undyed diesel fuel in stock that I previously purchased for sale. Do I need to pay a floorstock tax? Has the gas tax rate increased? What are the new refund tax rates for gasoline and diesel?