Australian Marriage Law Postal Survey

The Australian Marriage Law Postal Survey was a national survey designed to gauge support for legalising same-sex marriage in Australia. The survey was held via the postal service between 12 September and 7 November 2017. Unlike voting in elections and referendums, which is compulsory in Australia, responding to the survey was voluntary.

A survey form, instructions, and a reply-paid envelope were mailed out by the Australian Bureau of Statistics (ABS) to every person on the federal electoral roll, asking the question "Should the law be changed to allow same-sex couples to marry?" The ABS outlined processes to ensure eligible Australians lacking access to post could participate.

The survey returned 7,817,247 (61.6%) "Yes" responses and 4,873,987 (38.4%) "No" responses. An additional 36,686 (0.3%) responses were unclear and the total turnout was 12,727,920 (79.5%).

Prior to the survey, the Liberal–National Coalition government had pledged to facilitate a private member's bill to legalise same-sex marriage in the Parliament in the event of a "Yes" outcome. This allowed parliamentary debate and a vote eventually leading to the legalisation of same-sex marriage. Both the Coalition and the opposition Labor Party allowed their parliamentarians a conscience vote on the relevant legislation. Had the survey returned a majority "No" result, the government said it would not allow a parliamentary debate or vote on legalising same-sex marriage.

Many same-sex marriage proponents were critical of the postal survey, viewing it as a costly delaying tactic and an unnecessary hurdle to a conscience vote on same-sex marriage in the parliament. The survey was subject to two legal challenges questioning the authority of the ABS to conduct the survey and the government's right to fund the cost of the survey from funds designated by law for "urgent" and "unforeseen" circumstances. Both legal challenges failed; the High Court of Australia found that the survey was lawful.

Adults on the electoral roll in Australia as of 24 August 2017 were eligible to participate. By this date, 98,000 new voters had added themselves to the roll, which was a record high enrolment drive prior to a national vote. Survey forms were distributed from 12 September 2017 with the ABS encouraging returns promptly (preferably to be received before 27 October to ensure sufficient processing time). The survey closed on 7 November 2017 and the results were released on 15 November 2017. The Marriage Amendment (Definition and Religious Freedoms) Act 2017, which legalised same-sex marriage, came into effect on 9 December 2017.