A call to trust returning New Zealanders rather than hand them large bills.

A charge for new arrivals to quarantine appears to be a given - with National unveiling its plans to charge adults returning to New Zealand $3,000.

Labour has welcomed the opposition party's support for such a plan, with Minister in charge Megan Woods telling media the government is working through the legality of such a charge - and it will be discussed at Cabinet today. 

But, Auckland University experimental economics professor Ananish Chaudhuri thinks it's overkill.

He told Kate Hawkesby a better option could be a return to self-isolation, with better investment in contact tracing.

"Why not have much better contact tracing? You should be able to keep track of these people [and] ask them to show up for a three day and a 12 day swab test."

He says it's tough on those who left the country well before Covid.

"At no point did the Government tell these Kiwis 'if you don't return to New Zealand by this date, you will have to pay - for a family of four, with two kids above three, you will be paying $5,000'."

However, Infometrics Senior Economist Brad Olsen says if we don't charge, isolation is not financially sustainable.

"It means that we can continue to have people come over the border, without New Zealand having to make any harsh cuts to managed isolation facilities might be able to hold."