With the data of the de facto anonymised Income Tax Statistics 1998 (FAST 98), the German official statistics are for the first time publishing microdata from the field of fiscal statistics. The scientific community can use these data to analyse politically-relevant questions on the fiscal and transfer system at their own workplace, subject to the premises of article 16 subsection 6 of the Law on Statistics for Federal Purposes, on the basis of "real" assessment data. Passing on individual data to the scientific community is only possible in a de facto anonymised form. This form may impair possibilities for scientific analysis possibilities. So that anonymised data can nevertheless be used by the scientific community, anonymisation must meet two equal challenges: It must firstly guarantee adequate protection of the
individual items of data, and secondly it must optimally conserve the possibilities for analysis of the anonymised data. In order to achieve the right balance between these two goals, the Statistical Offices have involved potential scientific users in the anonymisation work in a research project.In the article entitled "De facto anonymised microdata file on income tax statistics 1998", in addition to the anonymisation concept the framework conditions of the project are explained and the analysis possibilities of income tax statistics demonstrated.