Supplemental environmental projects (SEPs) have received a growing amount of attention in recent years, from the Donald Trump Administration banning their use in settlements, to regulation and guidance from the Joseph Biden Administration reversing the ban, to legislative proposals prohibiting them altogether. This Article examines SEPs’ legality under existing law, focusing on claims that they violate the Miscellaneous Receipts Act and the Antideficiency Act. It begins with a brief history of SEPs’ policy evolution and the limitations on the U.S. Environmental Protection Agency’s and U.S.