By RNZ
One in five managed isolation bills has not been paid, according to official figures.
MIQ said it has sent out $170 million worth of invoices since the fees scheme started last year and $36m is overdue.
In August the amount of time returnees had to pay their bill was reduced from 90 to 30 days.
MIQ said that a debt collection agency has helped it recover about $1m of overdue fees.