Current discussions of possible tax reforms are characterized by an increasing relevance of related governments’ budgetary implications, thus, in this respect each tax reform proposal is reviewed in detail and an assessment of the consequences is essential from a political point of view. We developed the innovative micro-simulation model ASSERT (Assessing the Effects of Reforms in Taxation), which factors in changes in macro-economic conditions (GDP growth) as well as cross-border effects to analyze EU-wide tax reforms. To this end ASSERT is based on firm-level data, applies a forecasting algorithm and considers tax provisions for European countries. This paper presents the current version of the artifact as well as the development/evaluation process.