The coalition government appears likely to fall short of a Senate majority by five seats, but may not have to make deals with the Australian Greens to pass laws.
The coalition had 34 senators after the 2010 election and needed to gain five to hold a majority in the upper house from the half-Senate changeover on July 1, 2014.
On current projections, the coalition is expected to pick up three senators in NSW, Victoria, Queensland and Western Australia, two in South Australia and Tasmania and one each in the ACT and NT, leaving it with a total of 34.
Labor is set to hold two seats in NSW, Victoria, Queensland, Tasmania and Western Australia, with one each in the ACT, NT and South Australia, giving it a total of 26.
NT Labor senator-elect Nova Peris will be the first indigenous woman in parliament.
The conservative Palmer United Party's Glenn Lazarus is set to win a Queensland seat, with PUP's Jacqui Lambie on track to pick up a seat in Tasmania.
Independent Nick Xenophon will be returned in South Australia.
With the Australian Electoral Commission expected to count preferences on Sunday, the final NSW seat is a race between the Greens, One Nation founder Pauline Hanson, PUP and Labor.
In Victoria, the Australian Motoring Enthusiast Party could pick up enough micro-party preferences to slip ahead of the Greens.
The Greens' Scott Ludlam is likely to hold his WA seat.
Labor senator Don Farrell says he needs a "minor miracle" to hold onto his SA seat.
The final two SA seats will come down to the Greens' Sarah Hanson-Young, Xenophon party candidate Stirling Griffin and Family First.
Senator Xenophon says the process of "harvesting preferences" by the new generation of micro-parties needs to be examined.
The Liberals' Sally Chandler appears in contention in Tasmania, up against Ms Lambie from PUP.
Until the Senate changeover in July, the Greens will continue to hold the balance of power, making it impossible for the Abbott government to pass legislation such as the carbon tax repeal and toughening up asylum seeker policies unless Labor offers its support.