In December 1976 Ruding was nominated as an Executive Director of the International Monetary Fund (IMF), taking office on 1 January 1977.

In December 1980 Ruding was nominated as CFO and Vice Chairman of the Board of directors of the AMRO Bank, he resigned as Executive Director of the International Monetary Fund on 31 December 1980 and was installed as CFO and Vice Chairman of the AMRO Bank on 1 January 1981.

After the election of 1982 Ruding was appointed as Minister of Finance in the Cabinet Lubbers I, taking office on 4 November 1982.

In December 1999 Ruding was appointed as COO of Citibank Europe, serving from 1 January 2000 until 1 October 2003.

Following his retirement Ruding remains active in the private sector and public sector and continues to occupy numerous seats as a corporate director and nonprofit director on several supervisory boards (Centre for European Policy Studies, Society for Statistics and Operations Research, NIBC Bank, International Statistical Institute and the Tinbergen Institute).