The National Party is accusing the Government of "incompetence on a grand scale" after it was revealed more than 14,000 returnees who stayed in managed isolation and quarantine (MIQ) were not invoiced for their stay.
National's Chris Bishop uncovered the data after asking COVID-19 Response Minister Chris Hipkins about it in October.
Hipkins said at the time MIQ estimated "around 14,366 returnees are still to be invoiced for stays prior to 24 March 2021" and in addition, "there are approximately 7759 returnees for whom officials have not yet been able to determine whether, or how much, they should be charged".
The minister said the liability for these returnees added up to about $36.2 million on top of the $138.9 million in invoices that had been issued to returnees to that date.
The reason invoices were not issued came down to "incomplete or inaccurate data", according to Hipkins, who said a "new, more streamlined platform has been implemented".
"MBIE (the Ministry of Business, Innovation and Employment) has begun working through the backlog and emailing returnees about the liabilities they have incurred and then invoicing those returnees. MBIE expects these estimates will change over time as officials continue this process."
Bishop said in a statement that the figures were "incredible" and "reveal what a complete shambles the MIQ system is".
"This is incompetence on a grand scale and we need answers from the Government as to why the system is so shambolic," the National MP said. "MIQ was set up in a hurry so some teething problems could be expected, but it's now been running for 18 months.
"One industry that has experience in booking and billing systems, invoicing and extracting money out of people is the hotel industry - who the Government has actually partnered with in running the MIQ system. For reasons best known only to Labour, the Government decided to run the booking and billing themselves - and now we have a royal mess.
"These figures are emblematic of Labour's incompetent management of MIQ generally. What a shambles."
Hipkins told reporters on Tuesday morning that MIQ was "established in a hurry".
"Some of the systems and processes were a bit patchy in the beginning. I am satisfied the system has been fixed. Am I disappointed it took a while to get it to the point where invoices were being issued in a timely manner? Yes I am disappointed by that."
Asked if he thought the Government could realistically recover the $36.2 million, Hipkins said: "We will give it a good go".
"It does reflect the early stages of MIQ when it was set up in a hurry. The system is operating smoothly now, but it wasn't in the beginning. That is regrettable, but it is also understandable in the circumstances."
Joint head of MIQ Chris Bunny told Newshub it took "the recovery of the money owed for MIQ stays very seriously".
"Fundamentally it is taxpayers money and people should repay what they owe. It is our intention to invoice all those we are able to. The $36.2 million is an estimate of how much those invoices are worth, however we will not know the exact number until we have completed the invoicing. We expect this to be completed early in the New Year."
Bunny said MIQ's new invoicing platform provided the opportunity "to go back and look at those older cases that we haven't been able to process because of a lack of data".
"By way of history the MIQ invoicing process is very complex and was set up at pace - and at a time when it was unclear how long it would be needed."
He said the system was initially "heavily reliant" on manual processing of data coming from various agencies "that wasn't always accurate or complete".
"As a result, invoices haven't been issued as quickly as we would have liked, and there are some older cases we haven't been able to assess due to incomplete data."
As of November 7, 33,256 invoices have been issued, worth $152.9 million. Of this, $130.5 million is now due with $99.2 million paid. MIQ says 2594 invoices are more than 90 days overdue, worth $8.4 million, and debt collectors are following up on 1327 invoices, worth $4.3 million.