The New Zealand business growth was pushed up by higher premium growth in its retail business particularly through car and home insurance sold via its AMI brand.
Margins in the New Zealand business were also much higher with a 20 per cent underlying margin - up from 17.4 per cent in the last six months of 2017.
Its reported margin for NZ was 24.9 per cent after it saw a lower number of large claims and a benign period for "natural perils."
That compared to the underlying margin of its Australian business of 14.8 per cent which was also up from 11.4 per cent in the same prior period and a reported margin of 10.7 per cent.
Good news for IAG investors but not so good for those insured by the company - IAG is picking gross written premiums to be up by 2 per cent to 4 per cent of its full 2019 financial year which ends at June 30 and a reported insurance margin of 16 per cent to 18 per cent.