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A session of Parliament starts on the first sitting day following a federal election and ends when the Parliament is prorogued—formally closed—or the House of Representatives is dissolved—ended—for an election. The Governor-General acts on the advice of the Prime Minister to prorogue or dissolve the Parliament.
Section 6 of the Australian Constitution states that: 'There shall be a session of the Parliament once at least in every year, so that 12 months shall not intervene between the last sitting of the Parliament in one session and its first sitting in the next session.'
The term of a Parliament may include more than one session and constitutionally there is no limit to the number of sessions which may occur. However, in practical terms, the number of sessions would be unlikely to exceed 3 in any one Parliament (given that an election for the House of Representatives is required at least every 3 years).
In recent years, there has generally only been one session of Parliament per parliamentary term, with the 44th Parliament being an exception. However, in earlier times, parliamentary terms often included more than one session.