How can our system of preferential voting be changed?
Sample House of Representatives ballot paper.

Australian Electoral Commission
Description
This image is of a sample House of Representatives ballot paper. It includes the words 'House of Representatives Ballot Paper, State, Electoral Division of Division Name. Number the boxes from 1 to 8 in the order of your choice'. Below are 8 boxes with 'SURNAME, Given Names, PARTY' next to each. Some boxes also have a LOGO box next to them.
Permission should be sought from the Australian Electoral Commission (AEC) for third-party or commercial uses of this image. To contact the AEC email: media@aec.gov.au or phone: 13 23 26.
Hi Barry. Thanks for your question. There have been a number of changes to our electoral system since Federation. These include the introduction of compulsory voting, the lowering of the voting age and various changes to the way voting is conducted for the Senate and the House of Representatives.
Federal elections are organised and run by the Australian Electoral Commission who make sure elections are free, fair and legal. The Commonwealth Electoral Act 1918 and the Australian Constitution set out the requirements for running elections.
Further changes to our system can be made by alterations to the Commonwealth Electoral Act 1918. These changes would need to be agreed to by a majority vote in the Senate and House of Representatives the and given Royal Assent by the Governor General. This happened when the Commonwealth Electoral Amendment Act 2016 was passed by the Parliament changing the way voters elect senators.