Since the financial crisis, public awareness about tax havens and the issue of tax evasion and avoidance has dramatically increased. This was further amplified by the revelations of major tax scandals involving non-cooperative jurisdictions such as Luxemburg or the Bahamas and multinationals like Apple and Starbucks. At the European level, those developments reinvigorated the apparent willingness of decision-makers to take action, which translated in a series of initiatives addressing specifically the issue of corporate tax avoidance. I argue that these measures represent a major shift in EU policy-making in the field of corporate taxation and intend to explain both the nature of and the reasons for this policy change. Embedded in the constructivist tradition, my project draws upon the political science literature on ideas and discourse and the sociological literature on framing processes to show how the introduction of new ideas in the tax policy debate, such as transparency and fairness, enabled the policy change in European corporate taxation. Following a mixed-method approach, I propose to combine quantitative content analysis with process-tracing and expert interviews to identify the nature of and reasons for this policy change.