By the end of today, New Zealand will know if it has a new flag.
Voters are choosing between the current flag and the alternative blue-and-black Kyle Lockwood design in a second referendum that closes at 7pm tonight.
Preliminary results will be announced soon afterwards.
Prime Minister John Key said it had been a successful process and that he had always liked the Kyle Lockwood design but would not try to guess if it would be the winner.
The fact more than 2 million people had voted in the referendum was a good sign for change, he said.
"History sort of tells you a large turnout helps and you are seeing a lot more of both the current New Zealand flag and the proposed new flag flying around New Zealand - a lot more people discussing it.
"And in so much as this has been about New Zealand and the way we represent ourselves on the world stage our nationhood then I think it's been a success just getting that many people to vote.
Mr Key said he would not be disappointed in New Zealanders if the current flag was retained.