The office of the banking ombudsman reports a growing number of new complaints but says it is dealing with them faster.
In the financial year to 30 June 2011, the office received 1587 complaints, a drop of 18% on the previous year.
Most of that decrease is because thousands of complaints over the previous three years relating to the failure of the ING investment funds were resolved.
Banking ombudsman Deborah Battell says, once ING complaints are discounted, new complaints grew by 10%.
And she says her office cut the number of unresolved cases in the past year by more than two-thirds to 110 cases.
Figures show it helped more than 4,000 customers and arranged compensation from financial institutions of $3.8 million.