In order to address the fundamental challenges for the international tax regime brought about by the digitalization of the economy and new forms of potentially harmful tax competition, the G20 summit of October 2021 called for a commitment to the implementation of the Global Minimum Tax Proposal developed by the OECD within the framework of the Two-Pillar solution, aiming at 2023 as an implementation deadline. The breadth and technical complexity of the OECD Model Rules and the OECD Guidelines, as well as the Directive Proposal released by the EU Commission in December 2021, offer several inputs for further reflection, also considering the evolving international policy and political framework. The main purpose of this contribution is to highlight the most pivotal “known unknowns” of the proposed set of measures so as to stimulate further debate on the topic.