Ten million people are now estimated to have voted in the same-sex marriage survey and returned their forms.
The latest Australian Bureau of Statistics (ABS) figures show 62.5 per cent of survey forms have now been sent back.
That is up by 800,000 on last week when the bureau said 57.5 per cent of people had returned the survey.
The ABS is releasing a weekly estimate of how many surveys have been returned but it is not revealing any information about how many of those people have voted yes or no.
It is still more than a month until the result is announced on November 15.
Prime Minister Malcolm Turnbull has said there will be a vote in Parliament by the end of the year if the majority of surveys returned is for changing the laws to allow same-sex marriage.
Mr Turnbull said if there was a "no" result then there would not be a vote in Parliament.
The ABS has asked people to return their surveys by October 27 but says the final deadline is November 7.
The percentage of Australians to return their surveys is already higher than that of Americans who voted in last year's presidential election, which was 55.5 per cent.
And it has matched the turnout in last year's Irish referendum on same-sex marriage.
By comparison, 68.7 per cent of Brits turned out for June's general election.
