The party's Covid-19 Border Response spokesman and deputy leader Gerry Brownlee said this afternoon 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. This is a practical solution to a growing problem."
New National leader Judith Collins had confirmed the cost earlier today, saying the planned policy would likely be effective from October 3 if National won the general election on September 19.
"I want us to have a fair system ... it also needs to be compassionate," Collins told TVNZ's Q+A this morning.
Brownlee agreed it must be fair.
"Many Kiwis have only one or two overseas holidays in their lives. National won’t expect taxpayers to pay for other Kiwis returning from high-paying careers or expensive holidays in Europe.
“Those who need to return to New Zealand have had plenty of time to get home since border restrictions began, including through repatriation flights organised by the Ministry of Foreign Affairs. They will have a further two weeks to get home without facing the charge, after the election of a National Government on 19 September.”
In late June, Prime Minister Jacinda Ardern confirmed that the Government was considering part-charging those in managed isolation.
However, she said it was a "complex area" and legal issues that had to be canvassed. There were a number of Kiwis 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 tax payers 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 that 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 New Zealand 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."
