Newton-King joined the JSE in 1996 and became the executive director of the JSE in 2000. She was appointed to the board of the JSE in 2005 and became CEO of the JSE in January 2012, replacing Russell Loubser.[1][2] As deputy CEO she was involved in the introduction of affirmative action policies and an employment equity plan at the JSE. She was also responsible for their data vending business and eCommerce initiatives.[3]
On 28 October 2014 she became Director of World Federation of Exchanges.[2] She serves as a Member of the Financial Markets Advisory Board and the Presidential Remuneration Commission.[2] She serves as member of the King Task Group into insider trading and the Financial Markets Advisory Board, and helped draft the Insider Trading Act, 1998.[2][3] This statute provides for compensation for losses suffered as a result of insider trading. Since 2018 she has been a Non-Executive Director of Strate (Pty) Ltd.[2]