This move follows new EU regulation which has said that the roles of chairman and CEO must be separate.
Howard has been head of the firm since 1972, when he was managing partner of the business. From 1988 onwards, he was CEO and he has been chairman since 1999.
The company stated that although stepping down, he will continue as non-executive chairman. In the interim period he will continue in his role as CEO as part of the handover process.
Consultants have been appointed to work with the nomination committee on this assignment and a further announcement will therefore be made when the board is in a position to do so, Charles Stanley said.
Half-year results ending 30 September are expected to be reported in November.
