New Zealanders have collectively got more than $50 billion in their KiwiSaver accounts -11 years after the scheme was first launched.

Figures from actuarial research firm Strategic Insight show the amount of money in the retirement savings scheme rose 4.8 per cent between March 31 and June 30 from $48.5 billion to $50.8 billion.

A billion dollars flowed into KiwiSaver over the quarter from contributions while a further $1.3 billion came in from investment earnings and transfers from outside of KiwiSaver.

The biggest growth came from KiwiSaver provider Generate, which saw its funds under management rise 17.7 per cent to $837 million.

Generate is not a default scheme, which means it doesn't automatically get allocated any members from the government from those who are automatically enrolled.

Milford Asset Management also had strong growth with its funds under management rising 9.5 per cent to $1.22 billion.

While BNZ had the third highest growth at 8.3 per cent rising to $1.78 billion.

ANZ remains the largest KiwiSaver provider at $12.28 billion followed by ASB at $8.9 billion and Westpac with $5.77 billion.

KiwiSaver investors will get a boost to their accounts next month as the annual member tax creditor is paid into people's accounts.

The government contributes up to $521 annually - putting in 50c for every dollar a person contributes up to $1043.

KiwiSaver was launched in July 2007.