International tax coordination has reached impressive results after the turn of the century. Multi-lateral agreements like the Common Reporting Standard or the BEPS Action Plan are clear signs of the willingness of a large number of states to cooperate in fiscal matters at a global scale. Recently, the output of the Inclusive Framework on Pillar 1 and Pillar 2’s on the taxation of the digitalized economy has been celebrated as a major step towards an international tax order worth its name. This success story is strangely at odds with the visible fragmentation and de-globalisation of world politics where major actors like the United States, the People’s Republic of China, Russia or India are increasingly stepping back from multilateral commitments and assume a more confrontational stance. Against this background, this article tries to identify those characteristics of international tax rules that are necessary to deliver a reliable framework for international tax coordination. Two qualities stand out in this respect: “robustness” and “resilience” of international tax rules. “Robustness” means that the workability of a set of rules shall not be fundamentally called into question when one or two major players do not sign up to it or defect from the agreement at a later stage. Examples for “robust” arrangements are the transfer pricing rules based on the arm’s length standard and the concept of withholding taxes, while a worldwide formulaic system like “Pillar 1” does not meet this standard. “Resilience” means the capacity of a set of rules to be adapted over time given changes in the political, fiscal and economic environment. This kind of quality exists in the area of national legislation or when global “model rules” provide a non-binding template for bilateral or multilateral conventions. European legislation, on the other hand, has proven to be quite unflexible and prevents legislative change when necessary (as can be shown with respect to the Interest-Royalty Directive and the Anti-Tax-Avoidance Directive). This lack of adaptability might become a problem with the recently enacted Minimum Tax Directive
