Profit at KiwiBank has halved due to to a rise in provision for bad debts.
The New Zealand Post subsidiary made $21.2 million in the year to June, a decrease of 54% on the previous year.
The bank says lending and deposit growth remains strong.
However, the impact of earthquakes in Christchurch led KiwiBank to increase the amount of money set aside to cover bad debts quadrupling it to $79 million.
Chief executive Paul Brock says KiwiBank now has more than 750,000 customers and its underlying performance is strong.
Retail deposits rose 14% to $7.9 billion during the year, while borrowing rose 10% to $11.5 billion.
Customer deposits now account for 80% of all its bank funding.