In recent years, the multilateral world order has come to suffer from the resurgence of protectionism and great power rivalry that have fostered divergence and fragmentation in the global arena. Nonetheless, the growing interconnections between world economies and emerging global challenges, among which the COVID-19 pandemic, prove the need to enhance international cooperation to tackle common global challenges, thus making rival powers in certain areas strategic partners in many others. Addressing issues such as the COVID-19 pandemic, climate change or the fight against tax evasion, requires collective action and provides benefits for all participants. However, to foster action in this direction, rather than only focusing on the advantages of international cooperation, attention should be also posed to the costs of non-coordination. The lack of an unambiguous definition and specific assessment of the “costs” (not only economic) of global inaction in the face of common challenges may lead to sub-optimal policy decisions. We suggest calling on G20 leaders to set up an open and inclusive platform to share information and evidence on the costs of non-coordination, offering a bottom-up, flexible and open approach to multilateralism. In particular, we believe efforts should be devoted towards exploring avenues for the development of a comprehensive index on the costs of non-coordination. This approach could serve as a basis for identifying open “fit for purpose” forms of international cooperation, anchored to specific and practical issues. While international relations remain complex and often determined by national circumstances, providing more tangible information about the costs of non-coordination can yield more informed, transparent and accountable policy decisions.