There are concerns about the number of contractors using Kiwisaver being significantly lower than employees.
But an expert believes increasing government input to $2000 - up from $521 - could change that.
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Tom Hartmann is leading a working group on KiwiSaver, and says it's hard to entice self-employed people to contribute to the scheme.
"The incentives have to really encourage people to get engaged with it, and that's what makes it hard," he told Newshub.
Currently, the Government incentive is 50 cents on every dollar - up to $521 per year.
Hartman said contractors are missing out on free money by not contributing. He told Newshub the Government needs to provide incentive to those people.
The current incentive was not enough to prompt a behavioural change, he said.
"It's not really enough to incentivise behaviours - we have to convince people that they should pick up that free money."
A three-yearly review of retirement income policies is underway, with public submissions open until Thursday.