Prime Minister Malcolm Turnbull has confirmed that the government will try to hold a plebiscite on same sex marriage, and if the legislation is rejected a postal vote will be held over eight weeks from September.
The Australian Bureau of Statistics will run the ballot, and if a 'yes' vote is returned, same sex marriage legislation could be enacted before the end of the year.
The vote is expected to cost $122 million.
While there is concern about the ABS running the vote given the mess of last year's census, the government highlighted the fact that former PM Gough Whitlam used a postal vote regarding the national anthem in the 70s.
"At the last election, we made a very clear promise to the Australian people - that we would not facilitate the introduction of a bill to legalise same-sex marriage until the Australian people had had their say," Mr Turnbull said.
"And we made a commitment to give all Australians a say on same sex marriage.
"Since the election, we've come back into government, we've gone to the parliament, gone through the house, gone through the senate with a bill to enable compulsory attendance ballot - a plebiscite.
"That has been rejected by the senate.
"We will be presenting it to the senate again this week.
"But if that bill is rejected by the senate again, then we will hold a postal vote on this issue asking the same question, in which all Australians will have their say."