In-Lieu Fee (ILF) mitigation is one of the three primary mechanisms—along with mitigation banks and permittee responsible mitigation—that permittees can use to satisfy compensatory mitigation requirements. Through an ILF program, a permittee may satisfy their legal obligations under the 2008 Compensatory Mitigation Rule by purchasing credits from the program “sponsor”—a government or non-profit natural resources management entity—who then uses the funds to restore, enhance, or protect wetlands and streams. To date, ILF programs have implemented hundreds of compensatory mitigation projects across the country and many more projects are pending or in the planning stages. In addition, new programs continue to come online to provide additional compensation options for permittees. This report outlines the range of practice in ILF mitigation and describes innovative approaches across the country. Our goal was to support the development of effective ILF mitigation programs and enhance the capacity of state/local/tribal governments and others that develop or oversee ILF programs in order to improve the protection and restoration of watersheds and aquatic ecosystems across the country.