-        Of counsel at EY Tax Advisers (1992 - )

-        Co-initiator and -coordinator of the EUCOTAX Network (1992 -)

-        Co-initiator and -coordinator of the EUCOTAX Wintercourse (1992 -)

-        Co-initiator and -coordinator of the Brainstorm Group International Tax Law (1992-)

-        Co-initiator, -coordinator, and member of the board of the European Tax College (1997-)

-        Series editor of the EUCOTAX Series On European Taxation published with Kluwer Law International (1998 - )

-        Member of the Board and Research program leader of Center for Company Law (2002-)

-        Deputy Justice of the Arnhem Court of Appeal (Tax Division) (2007-)

-        Member of the Board of the PricewaterhouseCoopers International and European Tax Fund (2007-2013)

-        Member or editorial board of EC Tax Review with Kluwer Law International (2008-)

-        Peer reviewer of two international tax journals; titles not to be disclosed (2008-)

-        Coordinator International Business Taxation (2008-2017)

-        Vice-chairman Examination Committee of Tilburg School of Economics and Management (2009-2017)

-        Member of ECJ Task Force of the Confédération Fiscale Europeénne (2011-)

-        Head of Department Tax Economics (2013-)

-        Educational Coordinator Research Master Business, track Tax Economics (2013-2018)

-        Member of Advisory Commission EU Arbitration Convention for the Netherlands (2013-)

-        Member of Supervisory BoardKPMG Meijburg & Co Value Chain Management Fund (2013-2017)

-        Alternate member of European Commission Expert Group on removing tax problems facing individuals who are active across borders within the EU (2014-2015)

-        Member of UNCTAD Expert Group on FDI, Tax and Development (2014-2015)

-        Visiting professor at Wirtschaftsuniversität Wien (Vienna, Austria), Université de Panthéon-Sorbonne (Paris I) (Paris, France), Northwestern University (Chicago, USA), and Luiss (Libera Università Internazionale degli Studie Sociali, Rome, Italy), Katholieke Universiteit Leuven (Belgium), University of Florida (Gainesville, USA)

-        Guest lecturer at foreign universities, under which Universidad de Barcelona (Spain), University of Cambridge (United Kingdom), Universiteit van Gent (Belgium), Queen Mary and Westfield College (University of London) (United Kingdom), Universität Osnabrück (Germany), Università Degli Studi di Milano (Italy),  Università Bocconi (Milan, Italy), Universiteit van Antwerpen (Belgium)

-        Member of the Scientific Committee of Diritto e Practica Tributaria Internazionale (2003-)

-        Senior Fellow, Taxation Law and Policy Research Institute, Monash University, Australia (2006-)

-        Guest lectures at Dutch Ministry of Finance and Dutch Training and Study Centre for the Judiciary

-        Frequent speaker at (inter)national congresses, seminars, and courses

-        Member of Educational Board Tax Economics (2010-2012)

-        Short Term Consultant of International Finance Corporation (Member of the World Bank Group, Washington D.C., USA) (2004)

-        Member of academic and non-academic commissions

-        Visiting scholar New York University (spring 1999)

-        Teacher international tax law at the Federatie Belastingacademie (Nether­lands Tax Advisors Training Centre) (1991 - 1996)

-        Member of  Study Commission on the phenomenon of international tax avoidance of enitities of measures countering it (Commissie ter bestudering van het verschijnsel internationale belastingvlucht van lichamen, en van maatregelen daartegen) (1992 -1995)

-        Tax Inspector at tax inspectorates personal income taxes, tax inspectorate corporate income tax, tax accountants training centre; (1987 - 1991)