The Government appears to have reached an agreement about charging Kiwis who opt to travel overseas then go through managed isolation upon their return.

The announcement on the new legislation - which would need to be passed in the final two weeks of Parliament - could be as early as this afternoon.

The Government has been working through Crown legal advice about how to charge returnees with border facilities costing half a billion dollars by the end of the year without impeding the inalienable right to return home.

But any charge for returnees would require a law change.

Government ministers yesterday kept details of the legislation close to their chest but it appeared the governing parties had reached a consensus on charging New Zealanders choosing to leave for a short trip.

Prime Minister Jacinda Ardern was confident yesterday afternoon she would not have to reach across the House for National's support for the bill.

Ardern said "it was quite different" if someone chose to leave the safety of New Zealand "for something discretionary" than if a citizen or resident already overseas needed to come back.

"I think most Kiwis would agree with this, when you're already here in New Zealand and you're making a deliberate decision to go overseas - that's something quite different to someone overseas returning to New Zealand and there are different considerations there.

"I think there is some sympathy for New Zealanders who have lived and worked overseas who have found themselves caught up in this pandemic and through no fault of their own are now having to find themselves returning."

Ardern said there would be an announcement on the issue "very soon".

Cabinet Minister Megan Woods and Air Commodore Darryn Webb, who is in charge of operations at the facilities, have a press conference scheduled this afternoon.

The Greens are opposed to a blanket charge of all returnees but yesterday co-leader James Shaw said they were "open to" a co-payment for Kiwis opting to leave New Zealand for a short trip.

"There is a huge expat community - many of whom are stuck in a situation now where they're trying to get home and their visas are running out and we don't think that's fair."

It's widely estimated there could be up to a million Kiwis living overseas who all have the right to return at any time.

National leader Judith Collins said they also weren't opposed to charging returnees but wanted to see the legislation before giving it the tick.

National has previously announced it would charge people $3000 for a managed isolation room and an extra $1000 for an additional person and $500 for each child aged over 16.

"We do think it is important there are compassionate ground and medical grounds."

Meanwhile there was one new case of Covid-19 in managed isolation yesterday, meaning it's been 88 days since the last evidence of community transmission.

The Health Ministry was scrambling to contact-trace people who could have come in contact with a person who tested positive in South Korea after travelling there from New Zealand.

But because the person is a citizen of South Korea, health officials here have been unable to contact them but have been working with their counterparts to get more information.

Director general of health Ashley Bloomfield said there was no evidence the person caught Covid-19 here but they were working on a "worst case" scenario as a precaution.

The person, who was asymptomatic, tested positive after a rapid test which are not as reliable as the method used here and a second test has been ordered.

The person lived with five people in Auckland and all are self-isolating while they wait for their test results.

And contact-tracers are asking people who were two rows in front of and behind the traveller on flight NZ555 from Auckland to Christchurch on July 20 to self-isolate and get a test as a precaution.

Meanwhile anyone moonlighting between managed isolation facilities will need to stand-down between roles until they return a negative test.

It comes after revelations nurses had been working across different facilities.

Health Minister Chris Hipkins has ordered an independent review into managed isolation infection prevention.

Hipkins said while nurses were trained in infection prevention, there was "no room for complacency" and so from Saturday district health boards would take control for services rather than contractors.