Hung parliaments and democracy sausages: How your vote works

With the 2019 campaign officially underway, SBS News looks at Australia's electoral system.

Scott Morrison casts his vote in 2016. Source: AAP

On 18 May this year, Australians will head to the polls to decide who's going to run the country. But how does it all work?

Who can vote?

If you're an Australian citizen aged 18 years or older then you are required to vote.

But each election, it's up to every voter to make sure they are on the electoral roll and their details are correct. Otherwise, they cannot cast a ballot.

Voters at Bondi Surf Bathers Life Saving Club. Source: AAP

The roll closed last month and a record number of Australians are now enrolled to vote, according to the Australian Electoral Commission (AEC).

A total of 16,424,248 people, which accounts for 96.8 per cent of the eligible voting population, is on the roll.

This tops the number of people enrolled to vote ahead of the 2016 federal election by around 750,000.

What happens on election day?

While early voting is available for the upcoming election, most Australians will head to a local polling place on election day.

The obvious advantage of in-person voting is the availability of a "democracy sausage", or fundraising barbeques.

Bill Shorten eats a sausage sandwich on 2016 election day. Source: AAP

"If you're voting on election day in your home electorate, your name will be marked off the electoral roll and you'll be given a green ballot paper for the House of Representatives and a white ballot paper for the Senate," the AEC's Phil Diak told SBS News.

"The voting method for these ballot papers is different so it's very important to follow the instructions on the ballot paper."

The House of Representatives

The House of Representatives is also known as the "house of government", because whoever controls the chamber forms the government of the day.

Question Time in the House of Representatives. Source: Getty

"For the green House of Representatives ballot paper, you need to number every box with consecutive numbers from one through to however many candidates are on the ballot paper," Mr Diak said.

The candidate - representing the likes of Liberal, National, Labor, the Greens - who gets more than 50 per cent of the vote wins that electorate.

For the 2019 election, 151 people will be selected to sit in the House of Representatives.

Preferential voting

There's a big reason why voters need to number every box on their ballot paper.

"The Australian electoral system, unlike some of its counterparts overseas, is based on preferential voting," Mr Diak said.

"The intent of the preferential voting system is to ensure that the most preferred candidate, looking at all the preferences, is the one that is elected ... This comes into play when no candidate has achieved more than 50 per cent of the first preference vote."

So if no single candidate gets more than 50 per cent at the first count, the person with the least votes is eliminated, and the people who voted for them have their second preferences counted.

This continues until one of the candidates has more than 50 per cent of the vote.

How government is formed

The winning candidate from every electorate is tallied and the party with the majority of seats - that is, 76 - forms government and the leader of that party assumes the role of prime minister.

If neither party has enough seats to form government, it's called a hung parliament.

Political parties then approach other parties or independent members, and ask them to form a coalition.

This happened in 2010, when Julia Gillard had to form government with the help of crossbenchers.

What about the Senate?

There's also the white Senate ballot paper, which is far larger than its green counterpart.

The Senate is Australia's upper house or, "a house of review and a powerful check on the government of the day," according to parliamentary material.

Each state will elect six senators, while the Australian Capital Territory and the Northern Territory will elect two Senators, each.

Bob Katter with his ballot papers in 2016. Source: AAP

There are two ways to vote for the Senate - above the line or below the line.

If you want to vote above the line, you need to number at least six boxes for a party or group.

If you want to vote below the line, you will need to number the candidates in order of your first choice to at least your 12th choice

From there, you can continue to number the candidates in as many boxes below the line as you like.