Electoral system of Australia

The electoral system used for the election of members of the Australian Parliament is governed primarily by the Commonwealth Electoral Act 1918. The system presently has a number of distinctive features including compulsory enrolment; compulsory voting; majority-preferential instant-runoff voting in single-member seats to elect the lower house, the House of Representatives; and the use of the single transferable vote proportional representation system to elect the upper house, the Senate.

Source: Wikipedia — Electoral system of Australia (CC BY-SA 4.0)