This Special Issue is dedicated to honouring the contributions of Prof. Sol Picciotto, a champion for tax justice and a distinguished academic who has made significant contributions in the area of international taxation. In this Special Issue, the authors explore two prominent themes in Prof. Picciotto’s research: unitary taxation through global formulary apportionment and the internationalisation of the State.

Verónica Grondona discusses how theories of the state and its internationalisation provide a framework for discussing the challenges of international taxation. Prof. Reuven Avi-Yonah discusses what potential options exist for the United States, should global agreement on Pillar One fail to be achieved. Prof Kerrie Sadiq discusses formulary apportionment in the context of the extractive industry and how this may be employed to provide a fairer way to tax resource rents. Merlene Amonde and Salma Nechesa Abdulaziz discuss unitary taxation from the perspective of Africa’s extractive sector, and Kenya’s transfer pricing experience.

The Special Issue concludes with some reflections from Prof. Sol Picciotto himself. In his reflections, he highlights various aspects of his professional journey, from the initial motivation to study law and how that eventually led him to the quest to understand how multinationals are taxed, his championing of the unitary taxation of multinationals and the various other pivotal contributions he has made in the area of international taxation.

This Special Issue would not have been possible without the great efforts of the guest editors, Abdul Muheet Chowdhary and Tatiana Falcăo together with all the guest peer reviewers who provided invaluable feedback to the authors.