Voting has opened for the citizens' initiated referendum on smacking.
The poll asks: "Should a smack as part of good parental correction be a criminal offence in New Zealand?"
About 3 million voting papers will be delivered to mailboxes between Friday and next Friday.
The referendum voting process runs from Friday until 21 August.
Chief electoral officer Robert Peden is encouraging people to return their papers by 20 August to make sure they arrive on time.
It is the first time such a referendum has been conducted by post.