From midnight, those still in possession of prohibited firearms could face fines and up to five years in jail.
The Government's amnesty ends on Friday, with just under 60,000 guns now out of circulation.
But there are firearms owners across the country who still refuse to hand them in.
One of those owners spoke to Newshub under the condition of anonymity.
"They're law-abiding, upstanding people, and the moving of the goalposts has turned them into supposed criminals and it's not their fault," the man said. "It's not fair."
He's filed for an exemption to keep the gun as a collectible, but he's worried police may come knocking sooner.
"They're more than welcome to come get it," he told Newshub.
"That proves to me that a law-abiding citizen who is waiting to hear back if I'm going to be treated unfairly."
Since April, more than 56,000 banned firearms have been either professionally modified or destroyed.
Around $100 million in compensation has been paid out.
But critics are calling the process a failure.
"It's difficult to imagine how the police and Government could have screwed up worse," ACT leader David Seymour said.
That's something the police minister disputes - he has refused calls for an extension to the scheme.
"As of tomorrow, if someone does still possess one of these firearms then they face up to five years in jail and they certainly won't be getting any money for their weapons," Minister Stuart Nash said.
He said police will use their discretion whether to prosecute.