UPDATE September 12: This story has been updated to reflect the latest information on the postal ballot released by the Australian Bureau of Statistics and the outcome of the High Court challenge.
Check your mailbox, because the postal forms to vote on same sex marriage are being mailed out.
The $122 million postal survey is proceeding after the High Court gave the Government the all-clear last Thursday to proceed, just three business days before the mail-out was due to begin.
The Australian Bureau of Statistics (ABS) has scrambled to ensure every Australian will have the opportunity to vote, and has disseminated information on how to do so.
But just what is the postal survey (no, it's not a plebiscite), what will it mean for the marriage equality campaign and how do you take part?
The Prime Minister has said he wants every Australian "to vote in this survey, to have their say" -- whether it's what Australians wanted or not.
So, here is what you need to know to make sure your vote counts.
What Is The Postal Vote?
A plebiscite is a direct vote by all Australians on an issue -- in this case, marriage equality -- which doesn't affect the Australian Constitution (if it did, there would have to be a referendum).
But after the Turnbull Government again failed to push its plebiscite legislation through the Senate in August, the Government decided to side-step the Senate by opting to conduct a voluntary postal survey without passing legislation.
This means that, technically, the postal vote is not a plebiscite at all but an optional survey conducted by the Australian Bureau of Statistics (ABS) -- an organisation without the authority to conduct an actual plebiscite.
Similar to the now-defunct plebiscite, the postal vote won't be binding. This means that even if a majority of Australians vote 'yes' in the postal vote, it doesn't ensure same sex marriage will be legalised.
Instead, Turnbull says that a 'yes' vote will prompt a free vote based on a private members' bill in Parliament. A 'no' vote will not trigger this action.
Labor leader Bill Shorten has been pushing for this free vote without the stepping stone of a postal vote.
When Is The Postal Vote?
The voting forms will start being sent out on Tuesday September 13, and you will have just over six weeks to return the form to the ABS by the recommended deadline.
The final cut-off is 6pm on November 7, but remember, those forms have got to make it through the "snail mail", so don't leave it too late.
The deadline to ensure your enrolment details are up-to-date has passed, but if you didn't get to it this time around, you should still update them before the next election.
Tuesday, September 12 -- voting forms start being sent out
Monday, September 25 - all surveys should be received by this date. If you still haven't received your form, call the Australian Marriage Law Postal Survey Information Line.
Wednesday, October 11 -- requests to replace damaged or lost form closes
Friday, October 27 -- the date all Australians are strongly encouraged to return forms by
Tuesday, November 7 -- final deadline to return forms
Wednesday, November 15 -- survey results released
Who Can Vote, And Is It Compulsory?
Everyone who is registered on the Commonwealth Electoral Roll -- or who made a valid request for enrolment by August 24 -- is eligible to vote.
That includes Australians living or travelling overseas. However, contrary to earlier speculation, 16 and 17-year-olds aren't able to vote, as they can't vote in federal elections.
The postal survey is voluntary so whether or not you're correctly enrolled to vote, you won't face penalties for not filling out the form.
Voting rates among young people in particular are anticipated to be low, with one marriage equality advocate within the Liberal Party, Warren Entsch, saying the turnout of millennials could be as low as 30 or 40 percent.
At first, some marriage equality advocates expressed their intention to boycott the ballot process in protest against a vote which they argue is wasteful, non-representative and likely to lead to harmful campaigning.
But now, with voting definitely going ahead and forms in the process of been posted out, most marriage equality advocates have come out in support of the 'yes' campaign.
Former High Court Judge and outspoken marriage equality advocate, Michael Kirby, slammed the "irregular and unscientific" vote, initially saying he wouldn't "take any part in" it, although he later qualified to the ABC that, if the postal vote goes ahead, he would vote 'yes'.
Labor Senator Penny Wong has also urged people not to boycott the vote, despite labelling it just a "postal survey" which is a "stacked deck" against the 'yes' vote, arguing that this means marriage equality advocates have to work twice as hard to ensure it accurately represents the will of the Australian people.
So What Do You Need To Do?
Assuming you have updated your details on the Commonwealth Electoral Roll correctly, an Australian Marriage Law Postal Survey form will be arriving in your mail box some time from Tuesday.
The form will ask just a single question: "Should the law be changed to allow same-sex couples to marry?"
The letter will include a return paid envelope and instructions on how to complete it, so all you have to do is tick a box using a dark pen and post it back -- it won't cost you anything to vote. The ABS is encouraging voters to return their forms quickly, "Straight away, if you can!".
If you won't be at home during the weeks the forms are sent out, you can elect for the form to be sent to a different address by calling the Australian Marriage Law Survey Information Line.
The information line is 1800 572 113 and it's open seven days a week, 8am to 8pm (local time).
All the responses will be anonymous and the ballots will be destroyed within 60 days of the survey results being published on November 15.
But those contemplating filling their ballot envelopes with glitter have been issued with a stern warning from the ABS, which says it could lead to their ballot being destroyed and the vote not being counted.
"The survey envelope is... not a channel for correspondence, complaints or other communication," the ABS states on its website.
"Any extraneous material inserted in the envelope with the survey form will be destroyed and, due to processing machinery or possible contamination, may result in the survey form also being destroyed and therefore not processed."
What If You're Overseas?
Many Australians living, working or travelling overseas have expressed concern that the rushed process means they won't receive their postal vote, or that their vote won't make it to them and return to Australia in time to be counted.
As of August 22, the ABS has detailed special strategies put in place to ensure Aussies living in remote areas, those who don't have mailboxes and those living or travelling overseas will be able to participate.
This includes a priority mailout to Australians with less regular postal delivery, such as those in remote communities.
Australians who can't receive the postal vote by post, such as members of the homeless community, can pick up the form from advertised locations in every capital city, and some regional and remote locations across Australia.
If you'll be overseas at the time of the postal vote, the ABS is encouraging you to fill it out before you leave or when you get back, or to assign a trusted person to fill out your form on your behalf. But if that isn't possible, they will also be offering a paperless vote.
You'll need to request a Secure Access Code from the ABS -- either online or via their Information Line -- between September 25 and October 20. You can then use this code to provide an anonymous survey response online or on the phone.
A translation and interpreter service via the special information line will help Australians who don't speak English and the National Relay Service will be available to those who are deaf or have a hearing or speech impairment.
What About The High Court Challenge?
Until last Thursday, hanging like a rather pointy dagger over these proceedings were two challenges to the postal vote before the High Court, which had the potential for the highest legal authority in the land rule the postal vote as illegal.
Marriage equality advocate and independent federal MP Andrew Wilkie had asked the High Court to decide whether Malcolm Turnbull had the power to announce the postal vote.
They argued that the Prime Minister had overstepped his "executive powers" in ordering the ballot, because it has not passed legislation in Parliament ordering the $122 million poll be established and funded.
Another element of the challenges was the argument that the ABS is designed to collect statistical data (such as population ages, professions and hours of housework), and whether or not to legalise same sex marriage isn't a statistical analysis.
But the full panel of High Court judges dismissed the challenges, clearing the way for the postal survey to go ahead.
As news broke of the ruling, Prime Minister Malcolm Turnbull said he wants every Australian "to vote in this survey, to have their say".
"As I have said in this House and in many other places, Lucy and I will be voting yes and I will be encouraging others to vote yes," he told parliament.