Police say they're still working on plans for the collection and destruction of now prohibited firearms.
Deputy Commissioner Michael Clement told media on Thursday morning the prohibited firearms will be destroyed.
"For people who find themselves now in possession of a prohibited firearm, we ask you to please notify us online at the police website," Clement said.
"The collection of firearms will occur at a later stage."
Clement said an amnesty on owning now-prohibited weapons will apply for the next six months.
The Government announced a ban on military-style semi-automatic weapons and assault rifles in the wake of the Christchurch terror attack, and the Firearms Amendment Bill passed in Parliament on Wednesday night.
The changes were introduced after the alleged Christchurch gunman legally obtained assault rifles on an A Category gun licence - the standard license held by gun owners in New Zealand.
Changes exclude two general classes of firearms commonly used for hunting, pest control, stock management on farms.