Nicola Willis says National still hasn't decided on its superannuation policy ahead of next year's election.

The Finance Minister says keeping eligibility at 65 is increasingly expensive - and Prime Minister Luxon has expressed interest in making changes.

Willis says discussions will need to take place about the matter as a caucus.

"What that will look like will be different from the last election - because, obviously, 3 years have gone past since then. New Zealand, as we have pointed out in the past, is quite an outlier."

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