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 15:43 Related articles What are the new refund tax rates for gasoline and diesel? Has the gas tax rate increased? Has the undyed diesel tax rate increased? Is there a minimum purchase requirement in order to qualify for the government exemption from petroleum taxes? How do I register a diversion for motor fuel taxes?