The last federal election was held on 7 September 2013, and the 44th Parliament of Australia opened on 12 November 2013.  The first date that a normal House and half-Senate election can be held is 6 August 2016. The last date on which the next election can be held is 14 January 2017, which is calculated in the following way:
Section 12 of the Constitution says: "The Governor of any State may cause writs to be issued for the election of Senators for that State"
Section 13 of the Constitution provides that the election of Senators shall be held in the period of twelve months before the places become vacant.
Section 28 of the Constitution says: "Every House of Representatives shall continue for three years from the first sitting of the House, and no longer, but may be sooner dissolved by the Governor-General." Since the 44th Parliament of Australia opened on 12 November 2013, it will expire on 11 November 2016.
Section 32 of the Constitution says: "The writs shall be issued within ten days from the expiry of a House of Representatives or from the proclamation of a dissolution thereof." Ten days after 11 November 2016 is 21 November 2016.
Section 156 (1) of the Commonwealth Electoral Act 1918 (CEA) says: "The date fixed for the nomination of the candidates shall not be less than 10 days nor more than 27 days after the date of the writ".  Twenty-seven days after 21 November 2016 is 18 December 2016.
Section 157 of the CEA says: "The date fixed for the polling shall not be less than 23 days nor more than 31 days after the date of nomination".  Thirty-one days after 18 December 2016 is 18 January 2017.
Section 158 of the CEA says: "The day fixed for the polling shall be a Saturday". The Saturday before 18 January 2017 is 14 January 2017. This is therefore the latest possible date for the election.
The Coalition won the 2013 federal election with 90 of 150 lower house seats on a 17-seat 3.6 percent two-party swing, defeating the 6-year Labor government. Labor holds 55 seats while crossbenchers hold the remaining five.