Section 13 of the Constitution of Australia

Section 13 of the Constitution of Australia provides for three aspects of the terms of members of the Australian Senate, the timing of elections, the commencement date of their terms and for the Senate to allocate 6 and 3 year terms following a double dissolution of the Parliament of Australia. While member of the House of Representatives have a maximum three year term, members of the Senate have a fixed 6 year term, subject only to the parliament being dissolved by a double dissolution.

Senate elections must be held within one year of the expiry of the fixed term of the senate. The constitution originally provided for senate terms on calendar years, beginning on 1 January and ending on 31 December 6 years later. This was changed as a result of the 1906 referendum to terms beginning on 1 July and ending on 30 June, primarily to enable simultaneous elections to be held in March. The amendments were passed, being approved by 82.65% of voters with a majority in all 6 states. Despite the intention to hold elections in March, the first such Federal election was March 1983. Since 1906 section 13 provides that

In relation to the commencement of terms, there is a subtle difference between a half senate election and a double dissolution. For a half senate election, the election can be held up to one year before the commencement of the new senate term on 1 July, which means there can be a considerable delay between the election and Senators taking their seats. For example those elected at the 21 August 2010 election were required to wait 314 days before they took their seats. For a double dissolution, the terms are deemed to have commenced from the previous 1 July. This made no difference at the 2 July 2016 election where the backdating was just one day. The timing of the March 1983 election and May 1974 election meant that the "3 year" short term was less than 2.5 years.

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