This notice modifies Notice 2005-4, 2005-2 I.R.B 289, by revising the guidance relating to the Certificate for Biodiesel, which is required as a condition for claiming a credit or payment under sections 6426(c), 6427(e), and 40A of the Code. This notice also provides guidance on issues related to the boidiesel credit or payment that are not addressed in Notice 2005-4. This notice further modifies Notice 2005-4 relating to the Certificate of Person Buying Aviation-Grade Kerosene for Commercial Aviation or Nontaxable Use, which is required to notify a position holder of certain transactions under sections 4081 and 4082. Notice 2005-4 modified.