The twenty first century has seen a number of rapid developments in the international tax dispute resolution system, culminating with the Pillar One tax certainty block as proposed by the Inclusive Framework on BEPS. The present article provides an overview of these developments and assesses if the international tax dispute resolution system has achieved the long-desired stability, discussing the challenges posed from the perspective of low and middle-income countries as well as of taxpayers operating on a global scale. The research concludes that the current system may be viewed as an unfinished patchwork, which is why it does not meet the effectiveness, transparency, coordination, predictability, fairness and simplicity objectives needed to achieve stability. With this assessment, taxpayers and developing countries should focus on a comprehensive reform of the system. The article also calls for further research on the impact of international tax dispute resolution reform on the developing world.