A budgeting service believes there will be little benefit in the Opposition tax plan.
National is promising to link income tax brackets with inflation, and adjust them every three years.
"Assuming inflation of 2 percent, someone on the average wage would be $430 a year better off after the first adjustment, $900 after the second and $1,400 after the third," leader Simon Bridges said on Wednesday.
But Darryl Evans from Mangere Budgeting Services says the extra $8.20 a week in the first year will only have a minor effect - and it will be even less for lower earners.
"You could buy a loaf of bread, a carton of milk and a bottle of cheap cooking oil," he told Newshub. "As much as I am absolutely grateful for tax cuts, in the scheme of things it's extremely low."
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Mr Evans says the focus should be around the cost of rent - which can be up to 65 percent of a person's pay.
"I'm seeing families that literally every single time they have a rental re-do, the rent goes up - very often that's between $20 and $40 [a week]," said Mr Evans.
"I'm a great believer that every dollar saved in tax is great - I'm also a bit of a realist. I do have to ask, why now? Why didn't they do tax cuts over the last nine years?"
National adjusted the tax brackets and rates in 2010, changes which heavily favoured higher earners.
Labour has promised no changes to the tax scheme until after the 2020 election.