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 Has the gas tax rate increased? What are the new refund tax rates for gasoline and diesel? Has the undyed diesel tax rate increased? Who is entitled to the tare allowance for motor fuel taxes? What is the deadline for filing an omnibus refund claim for petroleum taxes paid on petroleum products that are subsequently sold to a government agency free of tax?