The FMA said it was responding to an increase in complaints and queries from would-be investors.
Complaints included customers being asked if they wanted to be able to access their KiwiSaver information online with their bank account information, without being told that would mean transferring to the bank's KiwiSaver product and that an application for credit would be looked on more favourably if the customer had a KiwiSaver account with the bank.
The FMA had also been alerted to banks signing customers up for a credit card, personal loan or other products and providing a KiwiSaver transfer form alongside other documentation for signing.
Such practices could lead to customers inadvertently agreeing to transfer their KiwiSaver to the bank.
Last year 149,407 New Zealanders changed providers, including more than 30,000 in November and December in the final two months of the year.
Given the level of competition, and pledges being made to would-be clients, David Boyle, general manager of investor education at the Commission for Financial Capability, which runs the Sorted website, said he expected that number to increase over the next five years.
"My concern is around people switching and not understanding why," he said. Some were changing schemes simply because providers offered the chance to see their fund's balance online.
That included banks that offered customers the chance to see their balance when they logged into online banking.
When asked by the Herald on Sunday this week, ASB, BNZ, ANZ and Westpac all cited offering KiwiSaver balances with online banking as a factor that might prompt people to switch.
But that shouldn't be a sole reason to switch, Boyle said, as most providers offered the ability to check balances online. The Inland Revenue Department allows savers to see what contributions have been made to their accounts.
"There should be more emphasis on providers ensuring the information is getting to customers before they switch, so they're switching for reasons other than convenience.
"Being able to see all their business including KiwiSaver in one place is not a really good reason to switch."
Bank schemes are among the most popular KiwiSaver programmes.
NZ Bankers' Association chief executive Kirk Hope said that was because clients already had relationships with them.
"The convenience that comes with bank providers is a factor that can't be ignored," Hope said.
"Many of us do enjoy being able to see all our accounts online at a glance, including our growing KiwiSaver balance. The performance of the banks' funds is also a factor worth taking into account."
Boyle said investors chasing better returns should be cautious before swapping schemes, as past returns were not a reliable indicator of future success.
The highest-performing funds would not necessarily suit every investor, either.
And some funds offering greater returns carried the greatest risk of tanking in a financial downturn. Careful switching would become more important as balances grew bigger. "It has to be a well-informed transfer," Boyle said.
We've only got one shot at saving for our retirement. So make sure your financial planning has more potential to soar than the native bird the KiwiSaver fund is named after.
