The research contributions to MaTax are based on a plurality of scientific approaches to ensure that the economic, legal, political and corporate constraints of tax policy are taken into account. Depending on the respective research question, specific models or approaches are chosen. MaTax projects particularly focus on microeconometric ex-post analyses to identify causal effects of implemented tax reforms and on microsimulation models (e.g. European Tax Analyzer, ZEW TaxCoMM, EUROMOD) to pursue ex-ante predictions of the effects of potential tax reforms. In addition, MaTax researchers use randomized field, survey and lab experiments to identify tax-related effects in a credible way using self-generated randomized variation. Wherever applicable, the underlying dataset consists of administrative tax data to ensure high quality and broad coverage (e.g., social security data, taxpayer-panel, ECB data). In addition, research projects will also be based on data collected at ZEW (e.g., tax paramenters, Mannheim Innovation panel, Mannheim Enterprise Panel). The quantitative studies are complemented by legal research to provide comprehensive tax reform analysis and guidance for future reforms.