Finance Minister Mathias Cormann understands a very large number of Australians have immediately returned their marriage equality survey forms.
"I expect it will be a credible participation rate," Senator Cormann, who has responsibility for the organisation of the survey, told Sky News on Sunday.
The Australian Bureau of Statistics, which is conducting the survey, will provide an update on the size of voting returns every Tuesday during October, ahead of the final result on November 15.
However, Senator Cormann reiterated it is the actual result of the survey, rather than the participation, the government will act on.
He says if there is a 'yes' vote, the government will facilitate a private members bill in the final parliamentary sitting fortnight before the end of the year to change the law to allow same-sex couples to marry.
Labor frontbencher Richard Marles, a long-time supporter of same-sex marriage, is not taking a "yes" vote for granted.
"If you do support marriage equality, you do actually need to fill in the form. You need to be encouraging your friends to do the same," he told Sky News.
"The contest is still very much an issue and it is in the realms of possibility that there is a 'no' vote."
Senator Cormann also dismissed media reports of a blowout in the cost of running the survey as "wrong", saying it was established at a cost of up to $122 million.
"I am very confident that we will be able to deliver this project in that envelope," he said.
