The potential economic benefits of offsets in a cap-and-trade policy may be critical for the success of a robust climate policy in the United States. The voluntary market, the international regulatory markets, and recent analyses of a possible U.S. market provide a foundation for our understanding of this important piece in the climate policy puzzle, but more work is needed. We introduce this series of policy briefs to provide in-depth assessments of remaining questions and concerns about how to best incorporate and benefit from sectors and actors that are outside of a regulatory policy.