More than four years have passed since the OECD issued the final version of the Action Plan to avoid Base Erosion and Profit Shifting (BEPS). In November 2016, the “Multilateral Convention to Implement Tax Treaty Related Measures to Prevent Base Erosion and Profit Shifting” – commonly referred to as the “Multilateral Instrument” (MLI) – was presented for signature. Based on BEPS action 15, the MLI was intended to modify more than 3,000 tax treaties to incorporate the treaty-related recommendations of the BEPS project and set limits to international tax planning. In June 2017, the MLI was signed by 62 states. As per the end of November 2019, the number has increased to 92 states. OECD officials described the MLI to be groundbreaking and a turning point in tax history. The actual state of the MLI implementation, however, shows a sobering picture. Stefan Bendlinger presents an interim balance of the MLI’s success and deals with the question whether the MLI can be a solution to put in effect forthcoming OECD projects such as Pillar I and Pillar II.