This research project on fiscal harmonisation within the WAEMU is first and foremost part of a context of regionalisation or the creation of stronger economic poles, between states in a global context of globalization. This study seeks to understand the thinking of the founding fathers of WAEMU in initiating such a process of fiscal harmonization. With the establishment of the Customs Union and the common market, dissonant tax practices, unfair tax competition, and investment incentive policies pursued by member states were not only contrary to the vision and objectives of WAEMU, but also compromised the smooth functioning of the common market, economic growth, and the expected socioeconomic development in the zone. Hence the need, indeed the urgency, to bring about a global convergence of domestic taxation in the States for a better control and management of national tax systems and public finances of the States. This research project aims to answer the central question of whether tax harmonisation is feasible and necessary within the WAEMU, considering that taxation remains a highly territorial matter that touches the heart of the fiscal sovereignty of States, to which the latter are ultimately very attached.