[4][5] The Malcolm Turnbull-led Liberal/National government went to the July 2016 federal election promising to put the issue of same-sex marriage to a national vote, in the form of a plebiscite.

[6] Despite narrowly winning the election, the government could not pass the legislation to establish the plebiscite in the Senate and so eventually decided to conduct a voluntary postal survey of all Australians on the electoral roll.

[12] The bill itself was the result of a cross-party effort following the reporting of a Senate committee in February 2017 which investigated how a same-sex marriage law with religious freedoms incorporated in it might operate.

[15] The terminology in the bill, specifically the wording "2 people" with respect to the definition of "marriage", alleviates the concerns of several transgender and intersex rights organisations.

[21][22] The bill addresses these concerns by defining marriage in Australia in gender neutral terms; "the union of 2 people".

[15] Though introduced by Smith, the bill was co-sponsored by eight other senators; Linda Reynolds (Liberal), Penny Wong (Labor), Louise Pratt (Labor), Richard Di Natale (Greens), Janet Rice (Greens), Skye Kakoschke-Moore (Nick Xenophon Team), Derryn Hinch (Justice Party) and Jane Hume (Liberal).

[24] In the Senate, several politicians sought to incorporate amendments designed to further religious, conscientious and other protections, in areas relating to marriages, classrooms and organisations.

[32] Subsequently, Senator Brandis and Canavan jointly moved two amendments (one to insert the words "nothing in this Act limits the right of any person...to manifest [one's] religion or belief in worship, observance, practice and teaching" and the other to extend a right of conscientious objection to civil celebrants).

The Labor Party opposed the first amendment on the basis that it "cherry-picked" elements of the International Covenant on Civil and Political Rights.

[36] During the second reading stage, Tony Abbott, the member for Warringah, moved an amendment to the bill which would have inserted the words "whilst not declining to give the bill a second reading, the House notes that it is vital that individuals and entities are not disadvantaged nor suffer any adverse effects as a result of conscientiously holding a particular view of the nature of marriage".

[27] Elsewhere, openly gay MP and same-sex marriage supporter Tim Wilson made history during his second reading speech when he proposed to his partner, Ryan Bolger, who was sitting in the gallery.

[39][40] On 7 December 2017, the amendment moved by Abbott was rejected by the House and the bill passed the second reading stage, in both cases without a division being called for.

[56][57] The Australian Capital Territory Government offered free marriage certificates for couples who married there under the annulled 2013 law, which was struck down by the High Court.