- In 2003 Tonko founded Dynamic Credit in New York and is CEO of Dynamic Credit Group and a (statutory) director of the licensed companies in group.
- Tonko started his career as a fixed income analyst in 1998. In 2000 he joined ABN AMRO Asset Management as an alternative fixed income portfolio manager, managing $250 million in institutional mandates.
- During the global financial crisis in 2008-2009 Tonko advised the Dutch Central Bank and the Ministry of Finance on the solution for the US mortgage issues ING Bank was facing on a $39 billion portfolio. This advice was subsequently examined by a Parliamentary Inquiry Commission and gave the taxpayer a positive return of €1.4 billion.
- Tonko studied Monetary Economics at the University of Groningen and continued his studies of Credit Risk Modeling at Stanford Business School in 2000.