President of the Institute of Tax Studies. Professor at the Faculty of Law and Administration of the University of Warsaw. From 1992 to 1996, he served as Deputy Minister of Finance responsible for the reconstruction of the Polish tax law system. During his tenure, among other things, the value-added tax and excise tax were introduced, excise products were labeled with revenue stamps, investment incentives in income taxes were implemented, and provisions on taxpayer identification (tax identification number) were developed. He also worked on projects such as the Tax Code and the Tax Advisory Act, as well as the concept of universal property taxation.

He is an academic lecturer at the University of Warsaw, the Warsaw School of Economics, and other universities. For 40 years, he has been delivering lectures and seminars on taxes and tax law. He has mentored many generations of tax specialists. He is the author and co-author of over a thousand books and articles mainly dedicated to taxes and tax law. He is a Tax Advisor and Legal Counsel. Member of the National Development Council under the President of the Republic of Poland. Honorary Chairman of the National Chamber of Tax Advisors. Member of the "Poland 2000 Plus" Forecasting Committee at the Presidium of the Polish Academy of Sciences.