The banking ombudsman says consumer complaints about the banking sector may be a lot higher than what's being reported.
Complaints about banking behaviour and service fell by 6.6 percent to 26,020 for the three months ended March.
The industry wide dashboard was set up last year in response to a regulators' review into the industry's conduct in 2018, which raised questions about the low number of complaints.
Banking ombudsman Nicola Sladden said the dashboard was still in its infancy and most of the banks were still developing how they received and reported complaints.
"I think the fact that this quarter reveals a 6 percent decrease simply indicates there's more work to be done to better capture all complaints rather than comment on the quality or the performance over the period."
A high level of issues being reported would indicate a high level of transparency between the banks and customers, she said.
The ANZ Bank was the subject of 46 percent of all complaints, despite having a market share of just under 30 percent.
ASB, BNZ and Westpac each had about 19 percent market share, but ASB received nearly 9 percent of complaints, and the other two nearly double that.
Kiwibank, which trails with just 4 percent of the market, had more than 6 percent of complaints.
Sladden said direct comparisons might not give an accurate indication of service levels because individual banks varied in size, had different processes for capturing complaints, and offered different products.
ANZ said the figures showed it did not sweep consumer complaints under the carpet.
"Our high number is because we're the largest bank and we have very thorough processes in place for voluntarily capturing and managing complaints - no matter how small," a spokesperson said.
"We believe that by voluntarily capturing complaints, and listening to what customers are saying, we can identify service issues and improve them."
The bank said it was one of the fastest in resolving issues.
Kiwibank said it also had a thorough process in place for handling complaints.
Just over half of complaints related to service issues, including long wait times at bank branches, failure to act as instructed, and slow responses.
Other issues raised by consumers were transaction errors, advice and fees.
Communication continued to be a common complaint theme, Sladden said.
"A lot of problems could be prevented with good, clear communication and information. When customers make a complaint, they want to be heard, understood, and responded to quickly."