Australia technically started its parliamentary elections with pre-poll voting on Tuesday, ahead of the July 2 elections.
"Anyone who can't make it to polling posts on the polling day can vote in the early voting," an Electoral Commission spokesman said.
"We expect one in four voters to vote in the early polls."
About four million voters are expected to cast their ballots in the early votes. In 2013, more than 3.7 million people voted early, representing 27 per cent of votes.
"It is important for voters to apply early to ensure there is enough time to receive their ballot papers, complete and return them to the AEC by election day," Tom Rogers, electoral commissioner, said.
The voters can visit early voting or mobile polling centres, or can also apply for postal vote, if they are genuinely unable to make it to the station in person on the day.
"Taking the opportunity to vote early for convenience or personal preference is not a valid reason under the Commonwealth Electoral Act 1918," Rogers said in a statement.
They are eligible if they live outside their electorate, if they are more than 8 kilometres from a polling post, if they are travelling or unable to leave their workplace to vote, or if they are ill or otherwise indisposed.
In Australia, voting is compulsory. Around 16 million people are enrolled to vote, almost a million more than the 2013 elections.
Australian political parties have been running their election campaign since May 9.
1,625 candidates are contesting the 2016 federal election, with 631 candidates for the 76 senate vacancies and 994 candidates for the 150 House of Representatives seats across Australia.
Prime Minister Malcolm Turnbull is leading Liberal party-led coalition effort with the focus on jobs and economic growth, while opposition leader of the Labour party, Bill Shorten, is focussed on education and health.
Latest polls have put the ruling coalition level with the opposition.
Turnbull and Shorten were to face off on Facebook this Friday in the first ever online debate, a local website news.com.au announced.
The third and final public debate between the two leaders will be streamed in real time via Facebook Live on the news website and its Facebook page.
"This debate will be different to any you’ve seen before," news.com.au managing director Julian Delany said in a statement.
"It is a chance for millions of everyday Australians to not just to watch the debate, but to actively participate — by asking questions and giving their instant reactions."