There are vote-saving provisions in the Electoral Act that allow some ballot papers to be included in the count even though the voting rules have not been fully met.
For House of Representatives ballot papers the requirement for a formal vote is that every square must contain a consecutive number for all candidates on a ballot paper to be a formal vote (see section 240 of the Electoral Act). This is the instruction that is printed on these ballot papers. However, there is a vote-saving measure that can operate where one square is left blank and where preferences for all other candidates have been marked with a consecutive number (see paragraph 268(1)(c)).
For Senate ballot papers the requirement for a formal vote is that when voting above the line, at least the numbers 1 to 6 shall be marked in the squares on the ballot paper (see subsection 239(2)). For voting below the line, the requirement is that at least the numbers 1 to 12 are marked in the squares printed on the ballot paper (see subsection 239(1)). However, there is a vote savings measure that can operate where only one square is marked above the line (see section 269), or where voting below the line, at least six squares have been marked 1 to 6 using consecutive numbers (see section 268A).
Counting the votes – Frequently Asked Questions - Australian Electoral Commission
Looks like they changed the rules (again). It used to be some number, say the first 3 had to be consecutive then if you spoiled the rest it'd still count (house of reps). They seem to have reined that in. Pity we can't demand partial preferential, it really is the best of all worlds....
I'm just a startled bunny in the headlights of life. L.J. Young.
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Wait! No one told you your government was a sitcom?