Inland Revenue (IRD) says around 750,000 tax refunds will be automatically generated next year for wage and salary earners who don't usually apply to get their tax back.
IRD Revenue Commissioner Naomi Fergusson said that, subject to legislation being passed, this would be the biggest change to individual tax in nearly 20 years.
Ms Ferguson said it hasn't been mandatory for wage and salary earners to fill out an IRD personal tax summary, but if they had and it had indicated a refund, they could have filed a return and received that refund.
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"In the new system all wage and salary earners' tax will be calculated and refunds sent automatically," she said. "About 110,000 more, who also haven't been filing, will have an amount to pay they'll be notified automatically."
"Getting a refund, if you're entitled to one, will be a whole lot simpler because it will be done for you," she said. "The only reason for contacting [IRD] now will be to tell us about any additional income information that we need to know."
She said the department will look at the data it has about an individual, and if it's confident there is enough information, IRD will "calculate and finalise their tax position for the year and generate an automatic refund".
"It will be very important that everyone has made sure the details we hold about them bank account number, contact details and so on are fully up to date so the new system works well for them," Ms Ferguson said.