Abstract. ISTAT is involved in various EU projects with the objective of "supporting the Lisbon objectives, EU governance and the process of national policy coverage with the best EU-wide and national policy impact and evaluation analyses". Existing knowledge on policy impact analyses is approximate. The "facts" on the impact of policies are charted only at the aggregate level and with a high degree of approximation. Macro indicators have well-known pitfalls and drawbacks. Understanding how policies affect economic performance and developing better indicators to gauge their effects is central to endow the EU with a set of efficient and fair policies. The gap in European knowledge and capacity for Policy Impact Analysis is patent. The DIECOFIS EU-FP5 project has taken up the challenge of reducing this gap in the field of taxation. Results have been quite encouraging and have open new vistas for future work. Particularly notable has been the development of a system of micro-founded indicators, based on factuals and counterfactuals, estimated through micro-simulation models. This has led to the current utilization of such a tool in the ex-ante microsimulation of the effects of several reforms of corporate taxation

Keywords: integration problems: enterprise performance; multisource database; microsimulation models; fiscal impact.