A new report examines the options for assessment and review of Parties’ contributions to ensure they are aligned with mutually agreed goals and principles, ensure transparency, and raise ambition over time. In 2013, Parties to the United Nations Framework Convention on Climate Change (UNFCCC) were invited to prepare and communicate their Intended Nationally Determined Contributions (INDCs) under a 2015 agreement. Assessment and review (A&R) of INDCs can help to ensure that these contributions are in line with internationally agreed objectives and principles, help establish and enhance transparency, trust and accountability between Parties, and raise ambition over time. This report examines the options for the design and organization of A&R under a 2015 agreement. The report analyses existing review processes under the UNFCCC and the Kyoto Protocol, and draws further lessons from reviews in intergovernmental processes outside of the UNFCCC, including the regimes for international trade, human rights, finance and ozone depletion. These reviews are complemented by an analysis of Parties’ views on A&R under a 2015 agreement.