Casual vacancies in the Australian Parliament

In the Parliament of Australia, a casual vacancy arises when a member of either the Senate or the House of Representatives:

A member will be disqualified if they are found to have been ineligible for election, or become ineligible to sit, because they:

A member will also be disqualified if they:

A member of the House of Representatives may resign by tendering the resignation to the Speaker, as required by section 37 of the Australian Constitution, or in the absence of the Speaker to the Governor-General. Similarly, a senator would tender the resignation to the President of the Senate or in the absence of the President to the Governor-General, as required by section 19 of the Constitution.

Casual vacancies are handled in different ways, depending on the house concerned.

When a Senate seat representing one of the six states becomes vacant, Section 15 of the Australian Constitution requires the parliament of the relevant state to choose a replacement. This is done in a joint sitting of the upper and lower houses (except for Queensland, which has a unicameral parliament). In the event that the state parliament is not in session, the Governor of the state (acting on the advice of the state's executive council) may appoint the replacement, but such an appointment lapses if it is not confirmed by a joint sitting within 14 days after the beginning of the next session of the state parliament.

Prior to 29 July 1977, it was an established convention, but not a constitutional requirement, that the state parliament choose (or the governor appoint) a replacement from the same political party as their predecessor. It had also been the practice for the relevant party to provide a list of suitable names to the state premier, and for the state parliament to make the choice. In 1975, both these conventions were breached - in the former case, twice.

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