Renewable energy certificates (RECs) are increasingly important—not to mention of significant economic value—in states that accept or require them as evidence of compliance with renewables portfolio standards (RPS). The emergence of RECs as a tradable commodity has made utilities, generators, and regulators increasingly aware of the need to specify who owns the RECs in energy transactions. In voluntary transactions, most agree that the question of REC ownership can and should be negotiated between the buyer and the seller privately, and should be clearly established by contract. Claims about purchasing renewable energy should only be made if REC ownership can be documented. The purpose of this report is to provide information and insight to state policy-makers, utility regulators, and others about different approaches to clarifying the ownership of RECs. We focus exclusively on three distinct areas in which REC ownership issues have arisen: Qualifying Facilities (QFs) that sell their generation under the Public Utility Regulatory Policies Act (PURPA) of 1978, Customer-owned generation that benefits from state net metering rules; and Generation facilities that receive financial incentives from state or utility funds.