The Electoral Commission has advised anyone who has not yet voted in the first flag referendum to get a wriggle on.
The latest figures showed 1,372,783 voting papers have been returned in the flag referendum, representing 43.3 percent of eligible voters - and tomorrow is the last day for people to vote.
Electoral Commission chief electoral officer Robert Peden said people could still get their votes in, by dropping it into a Post Shop.
"It's not too late to get your vote in but you really need to get a wriggle on and our advice is to take it to your nearest Post Shop and put it in the box there, just to be sure of getting it back on time."
But Mr Peden said the commission would still count the stragglers.
"Any voting papers that come through the post to us that are postmarked by the close of play Friday, the close of play tomorrow, that we receive by noon on Tuesday the 15th we are able to count," Mr Peden said.
The referendum is frequently described as Prime Minister John Key's pet project, and he was happy with where votes were at.
"Yeah, well, it looks pretty good, the understanding I had today is that it's 43 percent and tracking up obviously with a day or so to go, it shows you people are engaging.
"I suspect when we have the second referendum, which is really the run-off against the current New Zealand flag and the contender, you may even get more people turn out, but we'll wait and see."
In 2013, a postal referendum on asset sales saw a 45 percent turnout, while one on smacking children in 2009 saw a turnout of 56 percent.
The Labour Party has condemned the flag referendum, saying the $26 million price tag was simply too steep.
Leader Andrew Little said the turnout so far was high but his vote was not among them.
"Well, the ballot papers are [still] sitting there, I've started filling it out, or putting numbers, and I've got a day and a half to get it in the hands of the electoral officer, so I'll work hard to do that," Mr Little said.
He refused to say which was his favourite of the five alternative flags but said it was the inclusion of Red Peak that convinced him to take part.
His money was on New Zealanders voting to retain the existing flag in the second referendum in March.
New Zealand First leader Winston Peters predicted many of the returned papers would not even rank the flags
"I think they'll show from a lot of people a defence of the present flag even though its not part of the option choices that they have... they won't be spoiled, they'll be sending a message that they want the present flag that we have and that we've had since 1902."
Mr Peters said he wrote "keep our flag" on his ballot paper.
The voting papers are scanned by computers then double-checked by Electoral Commission staff.
Preliminary results are expected to be announced by 8.30pm tomorrow .
A second referendum will be held in March, where the most popular alternative flag will run off against the current flag.