Digital transformation has caused changes in all aspects of human life. In the DigiTax project, we look at the tax implications of this process from two perspectives. First, we examine the challenges that digitalisation brings to the tax area. For example, in the digital economy multinationals have more opportunities to shift profits to low-tax countries. Where should these profits be taxed? Also, increasingly robots are entering the labor force market, from automated driving cars to chatbots. Should they be considered a separate taxable entity, and if so, how do these robots need to be taxed? More generally, we will look at: (a) which tax regimes come under pressure, (b) is there a need to change the traditional tax concepts and if so which new tax concepts can be developed to contribute to a fairer taxation, (c) who is legitimately authorized, and (d) how to implement the change? Second, and vice versa, we study the opportunities that digitalisation creates for the fairness of taxation and the efficiency and effectiveness of the tax authorities. For example, how can improved data mining algorithms or the inclusion of novel data sources help to develop more accurate, understandable and discrimination-free fraud detection systems that minimize tax non-compliance or tax-evasion? Or how can blockchain technology improve transparency, tax compliance and trust between authorities and taxpayers? We will specifically look at the opportunities that data mining, internet of things (IoT) and blockchain technology bring to the tax domain. This project explicitly calls for a multidisciplinary approach, studying the technological, legal, economical and societal implications of digitalisation and tax.