New Zealanders have three weeks from Friday to cast their votes in the smacking referendum.
The postal ballot asks, "Should a smack as part of good parental correction be a criminal offence in New Zealand?"
Almost 3 million voting papers are being delivered from
The referendum has reignited debate over the controversial law, which was introduced in 2007.
It's New Zealand's first ever citizen initiated referendum held through the mail.
Chief electoral officer Robert Peden says voters simply need to tick "yes" or "no" on the referendum voting paper in response to the question.
To be included in the count, voting papers from within the country must be postmarked no later than August 21.
Voting papers from overseas must be postmarked no later than August 20.
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