; and (II) reduce any allocation of credits on the basis of that lifecycle evaluation. (D) Limitation (i) In general This paragraph applies only to retail electric suppliers that do not sell or generate fossil fuel energy in excess of the maximum allowable annual percentage of fossil fuel energy generation for the applicable calendar year, as determined under subsection (c). (ii) Prohibition The Administrator may not issue a fossil fuel energy credit for a calendar year to any retail electric supplier that exceeds the maximum allowable annual percentage of fossil fuel energy sales for that calendar year. (4) Credit banking A fossil fuel energy credit for any calendar year that is not submitted to comply with the maximum allowable percentage of fossil fuel energy requirement of subsection (c) for that calendar year may be carried forward for use in accordance with this section within the next 5 years, but not later than 2049. (g) Fossil fuel energy credit trading (1) In general A fossil fuel energy credit for any calendar year before 2050 that is not submitted to comply with the maximum allowable percentage of fossil fuel energy requirement of subsection (c) for that calendar year may be sold, transferred, or exchanged by the retail electric supplier to which the fossil fuel energy credit is issued or by any other retail electric supplier that acquires the fossil fuel energy credit. (2) Limitations (A) In general The sale, transfer, or exchange of fossil fuel energy credits may only occur between retail electric suppliers. (B) Rights A retail electric supplier shall be the only entity that may obtain legal rights to a fossil fuel energy credit. (C) Hotspots The Administrator shall— (i) evaluate trading to determine if trading results in the unsafe concentration of pollution in any area to any population; and (ii) if any unsafe concentration of pollution is identified, halt the sale of credits to entities— (I) within the identified area