Under the changes, voters will have more control over their preferences.
The general principles of the system are:
you have one vote;
you can express preferences for candidates in the order you prefer them, writing 1, 2, 3, 4, 5, 6 and so on; and
if the candidate for whom you vote "1" is not elected, the full value of your vote passes to the candidate to whom you gave your "2". And if that candidate is not elected, to your "3" and so on.
So, what do Australians need to know about the new system when they go to vote for their senators in this year's federal election?
Voting below the line
Below-the-line voters rank individual candidates in the order they prefer. The government's changes mean you have to number at least 12 squares below the line. But your ballot will nevertheless be formal provided it shows six consecutive preferences.
Suppose you are a Liberal voter but don't like the order of candidates as shown on the ballot paper. You may number the squares of the six Liberal candidates in any order – provided the numbers are sequential and each is different.
If you then want to preference the Shooters and Fishers candidates (numbering 7 to 12), then Palmer United candidates (numbering 13 to 18), but dislike the remaining parties, you may leave their candidates' squares blank. Your ballot is still formal and will be counted – as in the mock voting paper below.
Suppose you want to support particular candidates from different parties – and want to rank Penny Wong, Sarah Hanson-Young and Jacqui Lambie ahead of all the other candidates. You may certainly do that – again provided your ballot includes 1 to 12 and those preferences are sequential.
You might want to rank everyone except the main parties first. Let's say that you also prefer the Hemp Party and Socialist Alternative first, but then want to vote for the Shooters and Fishers. If you then think Labor is the least bad of the main parties, the best way to use your ballot is to preference all of the small parties' candidates and then Labor's. That way, even if all the smaller parties' candidates are excluded from the count, your next choice gains the value of your vote.
Note that you can rank the candidates of a particular party in any order. In the example below, the voter prefers Donald Trump to the other Shooters and Fishers candidates.
The more genuine preferences you express, the more likely a candidate you favour will be elected rather than one you disfavour.
The changes allow a vote to be formal provided that the first six consecutive numbers are 1, 2, 3, 4, 5, 6. If you omit or repeat a number, the ballot will still be counted. So a ballot that has the preferences 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13 would be formal – but only preferences one to nine would count.
Voting above the line
Voters are still able to vote above the line, where they rank parties – not individual candidates. If you put a "1" in the Liberal square, the first Liberal to gain from your vote will be (in our example) Malcolm Turnbull, the second Alexander Downer, the third Tony Abbott and so on.
A valid above-the-line ballot is 1 to 6, as in the following example, which places the major parties last. But this voter feels that if a smaller party doesn't get elected, the preferences should go in the order "Liberal – Labor – Green".
It could happen that when this voter's preferences are finally transferred, all the candidates for the first six parties chosen had been elected or excluded. The vote is then used to help decide the final contest, between Labor and the Greens – in this case favouring Labor.
An above-the-line "savings provision" means that even if you mark only one square, your ballot will still be counted. But (for example) if you mark the square for Climate Sceptics – and only that square – and the Climate Sceptics candidates fail to get enough votes to remain in the count, your ballot will become exhausted, meaning it will not count towards electing a senator.
This is why it is much better to express as many preferences as you can or want to – either below or above the line.
Image credit: AAP/Mick Tsikas