New Zealand Thursday began the final vote on whether to change its current flag to a new design featuring a silver fern.
The postal ballot will last for three weeks, and voters should receive their ballot papers in the coming week, electoral authorities said.
New Zealanders have a straight choice between the current flag, which shows the four stars of the Southern Cross and the British Union Jack, and the new design which features the same constellation but with a silver fern - a national symbol - instead of the British emblem.
The new design was selected by a public poll last year, which first selected a shortlist of five designs, and then narrowed down the finalists in several rounds of voting.
In the last round in December, the winning version beat off a rival suggestion featuring the same design but in the colours red, white and blue, by just 50.53 per cent to 49.47 per cent of votes.
Prime Minister John Key, a longtime supporter of changing the flag, has previously described the design as his own "number one choice."
Polls say New Zealanders favour retaining the current flag over switching to the designated alternative.
Preliminary results on the vote are expected on March 24.
The push for a new flag has been led by Key, who believes the current design represents a colonial era whose time has passed.
Many have criticised the cost of the referendum, estimated at 26 million New Zealand dollars (17 million US dollars).