When designing a policy, law, regulation or other type of “rule”, governments should always consider its likely effects. Regulatory Impact Assessment (RIA) provides crucial information to decision-makers on whether and how to regulate to achieve public policy goals. RIA examines the impacts and consequences of a range of alternative options. RIA also helps policy makers defend a decision not to intervene in markets where the costs of doing so outweigh the benefits. Regulatory Impact Assessment provides policy makers, civil servants and other public sector practitioners with a practical instrument for better designing and implementing RIA systems and strategies. The Principles cover a wide range of institutional organisations, tools and practices and present a list of critical steps as well as “dos and don’ts” for developing RIA frameworks. This report is part of the series OECD Best Practice Principles for Regulatory Policy produced under the auspices of the OECD Regulatory Policy Committee. As with other reports in the series, it extends and elaborates on principles highlighted in the 2012 Recommendation of the Council on Regulatory Policy and Governance.