40 CFR § 1051.705 - How do I average emission levels?
(b) Calculate a preliminary average emission level according to § 1051.720 for each averaging set using projected U.S.-directed production volumes from your application for certification, excluding vehicles described in § 1051.701(d)(4).
(c) After the end of your model year, calculate a final average emission level according to § 1051.720 for each type of recreational vehicle or engine you manufacture or import. Use actual U.S.-directed production volumes, excluding vehicles described in § 1051.701(d)(4).
(d) If your preliminary average emission level is below the allowable average standard, see § 1051.710 for information about generating and banking emission credits. These credits will be considered reserved until we verify them in reviewing the end-of-year report.
(e) If your average emission level is above the allowable average standard, you must obtain enough emission credits to offset the deficit by the due date for the final report required in § 1051.730. The emission credits used to address the deficit may come from emission credits you have banked or from emission credits you obtain through trading.