The KiwiSaver provider, operated by Pie Funds, launched in mid-2018 offering a tiered fee structure that steps up at certain balance milestones.

Someone with less than $5,000 invested has no fees, between $5,000 and $24,999 they are charged $60 a year, between $25,000 and $49,999 they are charged $180 a year, between $50,000 and $99,999 – $300 and balances over $100,000 are charged $600.

Morningstar said that was likely to be a unique fee structure in the market and meant that there was no way to represent the fee in the unit price or performance comparisons.

“This fee structure means that two investors with respective balances of $25,001 and $49,999 will both pay $180 per year. For the first investor, this amount would represent 0.72% of their investment balance, while for the second it would only represent 0.36%.”

Its performance was compared using a notional balance of $10,000 for this quarter's survey, which put it as a top performer with its growth fund, which returned 4%.

Morningstar noted that it had been a good quarter for markets. The S&P/NZX50 was up 4% and 24% for the year.

Australian shares were up 5.4% and the MSCI World Index was up 7.7% in New Zealand dollar terms.

There is now more than $60 billion invested in KiwiSaver, up from $51.7 billion at the end of September 2018.