SECTION 4. DETERMINATION OF

EMISSIONS RATES

.01 Most recent determinations under the 45ZCF-GREET model . Taxpayers must use the most recent determinations under the 45ZCF-GREET model for nonSAF and SAF transportation fuels. The term “the most recent determinations” means determinations under the latest version of the 45ZCF-GREET model (described in section 3.02 of this notice) that is publicly available on the first day of the taxable year in which the transportation fuel for which the taxpayer is claiming the § 45Z credit was produced. See also Notice 2025-10.

If a version of the 45ZCF-GREET model adds a type or category of fuel after the first day of a taxable year, taxpayers must use such version of the 45ZCFGREET model for the new type or category of fuel for the entire taxable year. Additionally, if an updated version of the 45ZCF-GREET model becomes publicly available after the first day of the taxable year of production (but still within such taxable year), then the taxpayer may, in its discretion, treat such updated version as the most recent version of the 45ZCFGREET model.

.02 Most recent version of CORSIA Default or CORSIA Actual . For purposes of § 45Z(b)(1)(B)(iii)(I), the term “most recent” means the latest version of CORSIA Default or CORSIA Actual (described in section 3.01 of this notice) that is publicly available on the first day of the taxable year in which the SAF transportation fuel for which the taxpayer is claiming the § 45Z credit was produced. Additionally, if an updated version of CORSIA Default

5 The 45ZCF-GREET User Manual, along with the 45ZCF-GREET model, is available at: https://www.energy.gov/eere/greet.

February 3, 2025 706 Bulletin No. 2025–6

qualifies under § 45Z(b)(1)(B)(iii)(II), instructions for how to use such methodology will be provided in additional guidance.

See section 4.06 of this notice if a type or category of SAF transportation fuel is not established in the most recent version of CORSIA Default or CORSIA Actual.

.05 Initial emissions rate table . The initial emissions rate table required by § 45Z(b)(1)(B)(i) is provided in the appendix of this notice. Each emissions rate determined under section 4 of this notice must be determined by calculating the lifecycle greenhouse gas emissions (as defined in § 211(o)(1)(H) of the CAA) for such type and category of fuel and must be expressed in kg of CO2e per mmBTU.

When calculating the emissions rate for purposes of determining the amount of the § 45Z credit, the taxpayer must accurately enter all information requested for the allowed methodology and must follow the publicly available instructions provided by the relevant authority (the DOE or ICAO). For example, a taxpayer calculating an emissions rate using the most recent determinations under the 45ZCFGREET model must enter all information requested within the interface of the 45ZCF-GREET model and must follow the instructions in the most recent version of the 45ZCF-GREET User Manual.

.06 Provisional emissions rate (PER) . Section 45Z(b)(1)(D) provides that for any transportation fuel for which an emissions rate has not been established under § 45Z(b)(1)(B), meaning a type or category of fuel that is not established in the most recent determinations under the 45ZCF-GREET model (for non-SAF transportation fuel) or that is not established in the most recent determinations under the 45ZCF-GREET model or the most recent version of CORSIA Default or CORSIA Actual (for SAF transportation fuel), a taxpayer producing such type or category of fuel may file a petition with the Secretary for determination of a PER.

A taxpayer requesting a PER is referred to as an “applicant.”

The Treasury Department and the IRS intend to provide guidance related to the PER petition process, including the process for obtaining an emissions value from the DOE that an applicant will use to request a PER determination, at a later time. The IRS will not accept requests for PER determinations for the § 45Z credit, and the DOE will not issue emissions values, until after such guidance is published. For purposes of the § 45Z PER process, an emissions value is a value obtained from the DOE setting forth the DOE’s analytical assessment of the lifecycle greenhouse gas emissions rate associated with the production of a type of transportation fuel using a particular primary feedstock and pathway.

.07 New emissions rates (including PER) apply on January 1, 2025 . The emissions rate for any new type or category of fuel established on the applicable emissions rate table or determined through the PER process will apply on January 1, 2025, regardless of when the Treasury Department and the IRS publish guidance establishing an emissions rate or PER.