On November 6-7, 2020, the 4th International Scientific Conference was held at the John Paul II Catholic University of Lublin. "Legal security of the state and the taxpayer and a fair tax system in the process of European integration: Poland - Slovakia - Ukraine - Germany". The conference - due to the epidemiological situation - was conducted via the MS Teams Platform. The organizers of this scientific event were: the Legal Commission of the Polish Academy of Sciences, Branch in Lublin, the Faculty of Law, Canon Law and Administration of the Catholic University of Lublin, the Faculty of Law and Administration of the Maria Curie-Skłodowska University in Lublin, the Faculty of Law of the University of Trnava in Trnava, the Faculty of Law of the State University of Internal Affairs in Lviv, the Alumni Association and Friends of the Faculty of Law of the Catholic University of Lublin, the Foundation of the Polish Academy of Sciences and the Faculty of Legal Sciences of the KUL Scientific Society.