Project R-13369

"Taxing for equality" in the personal income tax: the choice for a separate or joint tax unit? An interdisciplinary an explanatory study on the effect of international norms and organisations on the individualisation of personal income tax.. (Research)

In personal income taxation of EU Member States, a process of individualisation has been visible that started in the middle of the 1980s (Gunnarsson et al., 2017, p.27). This process of individualisation involves the tax unit a country applies in the personal income tax. Nowadays, states to a large extent use systems with individual or joint rationales. Where at joint tax units, the family as a whole is taxed, the individual is taxed at an individual tax unit. The tax unit selected by the state is in transition during the last decades. The focus of this research is to what extent this transition in personal income taxation could be explained by the role of international norms and organisations. This perspective is interesting, because together with the individualisation of personal income taxation, at first sight, there seems to be an increase of international attention for equality between men and women in personal income taxation, in which individualisation seems to be a target. In this interdisciplinary research, in which both legal and social science research will be combined, it shall be studied which legal norms international organisations create, how they speak about them, and in which way international norms and organisations potentially have had an influence on individualisation in personal income taxation. The main question of this research therefore is as follows: 'What is the effect of international norms and organisations on the individualisation of personal income taxation in the period 1984-2022?' In order to answer this main question, this research will globally consist of four parts. In the first place, the dependent variable will be described, i.e. the extent of individualisation of personal income taxation systems. Potential systems are described and multiple states will be classified. Secondly, the norms that international organisations have disseminated will be regarded, as well as the problem definitions of these organisations. With this, the independent variable is considered. In order to demarcate this research, four intergovernmental organisations will be studied, namely the United Nations, the European Union, the Organisation for Economic Co-operation and Development and the International Monetary Fund. On the one hand, relevant international legal norms (both hard law and soft law) that these organisations have created will be studied. On the other hand, it will be studied how these organisations spoke about these norms: what were their problem definitions? The goal of the third part of the research is to theorise about how international legal norms and organisations could have had an impact on the individualisation of personal income taxation. Based on social scientific theories (particularly theories of international relations), a theoretical framework will be formulated that clarifies how the independent variable could have had an impact on the dependent variable. This causal mechanism will be operationalised. In the fourth and final part of the research, this causal mechanism will be tested. By doing so, it is determined whether international norms and organisations really have had an impact on transitions in personal income taxation systems.

01 July 2022 - 30 June 2026