Simplicity managing director Sam Stubbs says some providers appeared to be disclosing only a fraction of fees in their annual member statements.
Many KiwiSavers are in the dark over the individual costs to manage their money because most providers don't give the full dollar figure in annual member statements.
KiwiSaver providers are required to send out an annual statement to members which typically show a person's account balance, contributions, annual member fee and tax paid.
But analysis of statements for the eight largest KiwiSaver providers show just three - Mercer, ASB and Kiwi Wealth - revealed the full dollar costs.
The other five providers - ANZ, AMP, Westpac, Fisher Funds, and SuperLife - disclosed member fees which ranged between $21 and $33 a year and AMP also disclosed a separate dollar amount for its admin fee.
But exactly how much individuals are paying for other fees is not made clear on the annual member statements - and those other fees are substantial.
Collectively the five providers declared $53.24 million in their annual member statements but left out $140.9m in other fees just for the year to March 31, 2016 alone.
Over the last three years fees not included in the annual member statement added up to $334.75m for the six providers according to their annual financial reports.
ANZ - the country's largest KiwiSaver provider - had more than 80 per cent of its fees not in its annual member statements.
While ANZ KiwiSaver members were told about $15.58m in member fees in their annual member statements the other $69.99m was not included.
That means a person with a balance of $31,472 in the ANZ default KiwiSaver conservative fund would see a $24 fee on their annual statement but will have paid $160 on top of that for other fees based on information in the scheme's annual financial report.
A spokeswoman for the ANZ said it clearly disclosed all fees charged in its investment statements.
"In addition, our periodic disclosure statements which are posted online every quarter clearly spell out the fees charged per fund. Our annual reports similarly spell out all fees."
The investment statement and quarterly statements show what percentage of a person's funds are deducted to pay for fund and management fees but not a personalised dollar figure which is dependent on how much an individual has in their account.
Conversely the annual financial reports contain a total dollar figure for fees for all members but do not tell individuals exactly how much of that they have paid.
The ANZ spokeswoman said the annual statements were intended to show members what their balance was at a point in time, along with a record of all transactions in their account during the year.
"The member fee ($24) shows on the statement because it involved a transaction to deduct it. The percentage-based fund fees form part of the unit price each day so don't show as transactions on the statement."
But she said the bank could be doing better.
"We agree that transparency on fees is important and we see room to improve our annual statements.
"We have been part of a working group which is considering a new format for KiwiSaver annual member statements and we'll be working to implement the changes that flow from this."
Fisher Funds managing director Carmel Fisher said its disclosure was in no way an attempt to hide the fees but reflected the fact the fees are charged to the fund and are not calculated at a client level.
"A member's KiwiSaver account is pooled with thousands of other investors and the fees they pay are in proportion to their share of the total fund invested."
She said her firm had looked at other providers' statements and spoken to its registry provider who had confirmed that "nobody discloses the total dollar amount".
A spokeswoman for NZX-owned SuperLife said the issue of fee disclosure was "complex".
"SuperLife have always believed in the principle of transparent disclosure. There are fees deducted from a member's KiwiSaver accounts, fees deducted from investment returns before they are credited to a member's KiwiSaver account, and fees deducted by third party investment managers before the KiwiSaver scheme receives the investment returns. It is not possible to show all fees on a member's statement," the spokeswoman said.
"SuperLife, like other providers, show the fees directly deducted from the member's accounts, and show other fees through the periodic disclosure statements. These are shown in a consistent format across providers," she said.
A spokeswoman for Westpac said the fee information in its annual statement was consistent with the current industry standard.
But Sam Stubbs, managing director of new KiwiSaver scheme Simplicity, said some providers appeared to be disclosing only a fraction of fees in their annual member statements.
"Perhaps that's because the real figure is embarrassingly high," said Stubbs.
The issue has been recognised by the Government which is working on a review of the annual statement in conjunction with the Financial Markets Authority and the Commission for Financial Capability.
David Boyle, group manager investor education for the Commission for Financial Capability, said it had been advocating for change to annual member statements to show the full dollar cost to members for some time and it was a priority for the review.
Recent research undertaken by the commission found 90 per cent of members would prefer to see a dollar figure on their annual statement.
"To me it makes sense - you want to know what you are paying for."
Boyle said it was really important that New Zealanders knew how much they were paying and what they were getting for that money.
At the moment most providers only show member fees which range around $20 to $40 a year on the annual statement.
"Probably a lot of New Zealanders think that is their total cost," Boyle said.
Some providers also showed a percentage charge for particular funds on the statement but Boyle said a lot of people would not know what that was for or how to work out exactly what they were paying from that figure.
"That is why we are advocates of the total dollar costs."
He said there was no reason why providers could not show the total dollar value for fees in annual member statements.
"I suspect it [the full cost] will be a bit of a surprise for many."
Paul Goldsmith, Minister of Commerce and Consumer Affairs, said it was his goal to introduce new regulations in time for the next round of annual member statements which typically come out in April and May.
Those regulations would allow people see what their balance might be at retirement and the kind of income that could give them as well as ensuring the total fees were fully accounted for in dollar terms.
Goldsmith said he was disappointed providers were not already disclosing that information, particularly in the annual member statement which were what most consumers looked at.
He said a lack of government regulation requiring it was no excuse for providers.
"I think most KiwiSaver consumers would expect to have fees outlined in their entirety. Frankly, if people are concerned they should get in touch with their provider."
He blamed a heavy regulatory programme on the Government's slowness to address the issue.
"There has been a colossal amount of regulatory change in the financial services area. This is the next thing to deal with."
"It is my desire and expectation that it will be in place for the next annual statements - at the very least in a percentage form."
• An earlier version of this story said only two (ASB and KiwiWealth) out of eight providers gave the full dollar figure for fees in annual members statements but Mercer also gives this information. All figures have been updated to reflect this.