Before announcing the postal survey, Prime Minister Malcolm Turnbull pledged that if the result in the postal survey was a yes, then he'd seek to introduce legislation to legalise same-sex marriage by Christmas.
The latest polls suggest more than 60 per cent of people have voted yes.
Debate on the Bill begins tomorrow and resumes when Parliament returns in the last week of this month.
Almost 80 per cent of eligible Australians took part in the voluntary poll and the outcome will be announced by the Australian Bureau of Statistics at 10am on Wednesday.
Australia has become increasingly isolated among Western nations on same-sex marriage, with Germany, the USA and Ireland recently joining countries including the United Kingdom and New Zealand in legalizing unions.
Italy legend Gianluigi Buffon 'confirms retirement from global football'
Unfortunately for the Lazio frontman, he was forced to shoot from a tight angle and could only fire into the side-netting. It's the first time the Swedes have made the World Cup since 2006, leaving just three spots to still be decided.
Cabinet minister Simon Birmingham has described the Smith bill as a "logical starting point" for a parliamentary debate on same-sex marriage.
With a turnout of 79.5%the result in the voluntary survey is considered a highly credible reflection of Australian opinion and gives marriage equality advocates enormous momentum to achieve the historic social reform.
Nevertheless, discussions are well under underway as to how same-sex marriage might be legislated.
A second private bill, containing more protections for religious protections and conscientious objection, is being pushed by conservative coalition MPs, many of whom campaigned for a "no" vote.
"I'm sure you will all applaud the authenticity and the passion that will come into the different views", Mr Turnbull said. But there's still a key question: if the country does the right thing and votes Yes, when will we actually get marriage equality? Ironically to ensure these protections, the bill would override existing state and territory anti-discrimination and freedom-of-speech laws.
Liberal senators Linda Reynolds and Jane Hume, Labor's Penny Wong and Louise Pratt, the Greens' Richard Di Natale and Janet Rice, Skye Kakoschke-Moore from the Nick Xenophon Team and Derryn Hinch all signed the motion with Smith. "I don't think this survey was a vote on expanding the capacity to discriminate in our society".