Anyone entering New Zealand from October 3 would be charged a $3000 fee per adult for their managed isolation if National wins the election.
The party's Covid-19 Border Response spokesman Gerry Brownlee said the fee would be used "partially meet the costs of their quarantine".
Each adult would be required to pay $3000 per adult towards the cost.
Additional adults in a room if a couple had arrived would be charged an additional $1000.
Children under 3 years will have no cost and over 3 years will see an additional $500.
"Currently taxpayers are funding a long and very expensive government response to let people come into the country. It's entirely fair that those who benefit pay a share," he said.
"This fee is for the purpose of cost recovery to reduce the burden on New Zealand taxpayers, and to cover some of the costs of accommodation and food over the 14 days of required quarantine for persons entering the country."
Brownlee said there could be exemptions on compassionate grounds but only for New Zealand citizens and permanent residents.
National's policy was similar to that used in New South Wales, Queensland and South Australia, he said.
"Two-week quarantining looks likely to be with us for a while," Brownlee said.
"This is a practical solution to a growing problem."
New National leader Judith Collins had confirmed the cost earlier today. The planned policy would likely be effective from October 3 if National won the September election.
"I want us to have a fair system ... it also needs to be compassionate," Collins told TVNZ's Q+A this morning.
She said the proposed fee would be "around" $3000 with "some exemptions".
"Gerry's going to be announcing it all, he's got all the detail, and he's the spokesman on it," Collins said of her deputy Gerry Brownlee.
In late June, Prime Minister Jacinda Ardern confirmed the Government was considering part-charging those in managed isolation.
But she said it was a "complex area" and legal issues had to be canvassed.
She said New Zealanders were coming home "for a range of very significant and often dire circumstances".
"I'd say if you're making the choice at your expense to travel overseas, then you should meet the full cost of that holiday," she said.
"My view is that if you're making the choice to go on a holiday offshore with the expectation that taxpayers pick up the tab on your return, that it's right for us to look at whether or not we can deal with that.
"Not only does it put extra pressure on our system for New Zealanders who need to come home, you actually have a choice over whether you leave or not."
Ardern said the Government would move "cautiously" on the matter.
The next day Megan Woods, the minister in charge of managed isolation, spoke further on the matter.
She acknowledged New Zealanders had a legal right to return home and could not be stopped.
"That's what we're working through ... and it could well require legislative change," she told the Herald.
"One of the things we also need to make sure is that we're essentially not setting up a test for New Zealanders based on how much money they've got in their bank account.
"We'd have to make sure we had hardship measures in there as well ... that people can pay it back over a period of time, for example."