The FTSE 250 group said it expected net trading revenue to be £250mln for the six months to 30 November, compared to £251mln last year.
This meant that revenue was down to £120.9mln in the second quarter, compared to £129mln in the first quarter of this financial year and £122.1mln in the second quarter last year.
The industry has been hit by leverage limit regulations brought in across the UK and EU from 1 August last year.
IG said it had “continued to build the size and quality of the active client base in its core markets, which is the key driver of revenue growth in the medium term”.
While core market revenues are expected to be down 6% to £210mln, it served an average of 78,500 over-the-counter leveraged clients per quarter in its core markets in the half-year, up 4% on the second half of last year.
IG said the reduction in these core revenue was due to the prior year period including two months of trading prior to the implementation of the ESMA measures, and the lower level of trading by professional-rated clients in the past quarter compared to a strong comparative last year.