The first wave of microsimulation development at TÁRKI was carried out in 1995. Since then, model-building and IT development have been performed on a contractual basis, at the request of the Ministry of Finance. For the most recent wave, the Ministry of Health, Social Affairs and Family joined in, too. After statistical matching to anonymised microdata from tax records (bought from the tax authorities) and to consumption records (purchased from the Central Statistical Office), the Monitor database is incorporated into the TÁRSZIM microsimulation model. The model is used by the government for ex ante impact analyses of planned tax and benefit measures.