The Indigenous Voice to Parliament referendum will not pass, with Australians set to vote against enshrining the body and recognising First Nations peoples in the Constitution today.

While the official result is still days away from being announced by the Australian Electoral Commission (AEC), a No vote across the country means the required double majority for the referendum to succeed looks an electoral impossibility.

As of 7.30pm, there seems to be no path to victory for the Yes vote with NSW, South Australia and Tasmania set to deliver a No vote.

REFERENDUM: Follow our live results tracker here

Now the result is all but known, Prime Minister Anthony Albanese is expected to address the nation from Canberra shortly in a call for unity across Australia following the divisive campaign.

Opposition Leader Peter Dutton will not speak tonight.

Before polls had closed, Albanese declared "I've done all I can" for the Yes vote when he made one final appeal to undecided voters.

LIVE UPDATES: Voice to parliament referendum defeated

"This is not a radical proposition," he said from a polling centre in Balmain, Sydney.

"This is a hand outstretched of friendship from the first Australians to every Australian, just asking for it to be grasped in that spirit of reconciliation and friendship."

Opinion polls had consistently shown support for No had outweighed Yes voters in the months and weeks leading up to referendum day, and proved to be an accurate prediction of how the nation would vote.

That was despite a mammoth army of volunteers supporting the change – according to Yes23 director Dean Parkin, more than 80,000 contributed to the campaign today.

Leading Yes campaigner Thomas Mayo told 9News supporters of the constitutional change had thrown everything at the referendum.

"There has been so much hard work and I don't think that we could have done anything different," he said.

"I think there will be analysis later and we will see what those numbers have to say, but one thing is for sure, the No campaign has run a dishonest campaign, a lot of disinformation.

"But for us we have done everything right, we told the truth about what this is: simply recognition and listening to Indigenous people."

That claim was rejected by No campaign leader Warren Mundine.

"We hadn't done anything wrong," he said.

"We have been clear on our messaging and our honesty in this whole campaign… we always had faith in the Australian people, we always believed in Australian people.

"But what we've got to do now, whatever the final result is tonight, what we've got to do is wake up in the morning and we've got to pull together as a nation, pull together as people and actually do the hard yards that need to be done."

The result continued the trend of referendums requiring bipartisan support to succeed; of the 45 votes to alter Australia's Constitution, only eight have succeeded, all of which were backed by the government and opposition.