The bank's net profit in the June quarter rose to almost $5 million from $2.33 million in the same quarter latest year, bringing its annual result to $15.8 million compared with $7.2 million last year.
Net interest income was up 50.3% to $15.2 million in the latest quarter and other income was up 30.1% to $26 million while operating expenses rose only 28.6% to $33.6 million.
Kiwibank's share of the mortgage market rose by $250 million to $2.51 billion during the quarter, taking its market share from 1.91% to 2.05% at the end of March. At the end of June last year, its mortgage book stood at $1.53 billion giving it 1.43% of mortgages written by registered banks.
Kiwibank chief executive Sam Knowles says his bank is aiming to increase its mortgage market share by about a percentage point a year.
ASB Bank, now New Zealand's largest bank (classing National and ANZ as separate banks although ANZ owns both), is "a good role model" in that it was quite small 15 or 20 years ago and has grown organically, Knowles says.
Kiwibank has overtaken both HSBC and TSB Bank in terms of market share. While it is the fifth biggest bank, but it is still a long way fourth placed Bank of New Zealand, which claimed 16.27% of the market at June 30.
Neither NZ Post nor the government has imposed any limits on Kiwibank's growth, Knowles says.
