Timely and reliable fiscal data is crucial to the effective and efficient monitoring of government policies on tax expenditures in general, and on energy tax expenditures in particular. In this regard, European Council Directive 2011/85/EU obliging Member States to introduce domestic provisions for the publication of detailed information on the impact of tax expenditures on revenues ensures the regular public availability of tax expenditure data to monitor the energy tax incentive policies of all 28 countries. The basic level of transparency underwritten by the Directive allows tax policy to be scrutinized by academics and civil society across Member States, which in turn raises the quality of data available. To exemplify this, we present a case study of Turkey, which began publishing detailed tax expenditure reports in 2016. This publicly accessible data has enabled us for the first time to measure how and to what extent the government is supporting the energy sector through tax incentives in Turkey.