The specialist bank said group operating profit for the year to 31 March will drop 7-14% on last period’s £732mln.
Net asset value is expected to be 425-450p, while last year it was 434.1p.
The firm had £12.4bn in the bank as of Wednesday, representing 40% of customer deposits.
Its asset manager arm Ninety One completed its demerger earlier this week, although Investec did not sell its 10% stake in the new entity due to market volatility and its “already comfortable capital position”.
Investec added the demerger increased capital levels and reduced risk.