10 CFR §490.507

1. (a)Any fleet or covered person that is required to acquire alternative fueled vehicles may transfer an alternative fueled vehicle credit to—
   1. (1)A fleet that is required to acquire alternative fueled vehicles; or
   2. (2)A covered person subject to the requirements of this part, if the transferor provides certification to the covered person that the credit represents a vehicle that operates solely on alternative fuel.
2. (b)Proof of credit transfer may be on a form provided by DOE, or otherwise in writing, and must include dated signatures of the transferor and transferee. The proof should be received by DOE within 30 days of the transfer date at the Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy, EE-2G, 1000 Independence Avenue SW, Washington, DC 20585-0121, or such other address as DOE publishes on its Web site or in the Federal Register.