In 2009 the members of the Group of 20 (G20) proclaimed the forum to be the premier body for their international economic cooperation. But the G20’s success in facilitating such cooperation is mixed. The G20’s immediate response to the 2008 financial crisis was considered to be a success, but its effectiveness has waned since then. There are, however, two aspects of business regulation where the G20 has successfully facilitated international cooperation to achieve significant outcomes that have affected the business climate in G20 members. These are the efforts to strengthen financial regulation and to modernize the international taxation system. This article identifies the characteristics that have contributed to the G20 achieving greater progress in these two areas, how these differed from other issue areas and the lessons that can be derived for the G20. Some of the key points identified for the G20’s relative success with financial regulation and international taxation include: broad agreement in advance on the underlying problem and solution; agreement on a common course of action for each member; agreement on a mechanism to monitor compliance; the presence of domestic public pressure on countries to act; and the continuity provided by successive G20 chairs.