The Australian Electoral Commission confirmed on Thursday the duo are the two successful candidates for the territory in last month's federal election, and will formally declare their victory on Friday afternoon.

Senator Seselja has been in the upper house since 2013, after nine years in the ACT legislative assembly.

His Labor counterpart - a former ACT chief minister - is returning to the Senate, where she sat for three years before being ruled ineligible in 2018 over dual citizenship.

The electoral commission also revealed on Thursday that Jacqui Lambie, who was also forced to leave the Senate upon discovering she was a dual citizen, will return to represent Tasmania.

"I've been keeping my fingers crossed and the count has been looking positive for us since election night, but I have been careful to keep a lid on things until the result was official," she said.

The new parliament will sit for the first time on July 2 and Ms Lambie anticipates a whirlwind effort before then to get her office back up and running.

The state also elected Liberals Richard Colbeck and Claire Chandler, Labor's Carol Brown and Catryna Bilyk, and Green senator Nick McKim.

The sole newcomer is 28-year-old Ms Chandler, who is aiming to reach out to a new generation of voters.

Labor senator Lisa Singh, who successfully campaigned for a below-the-line vote in 2016, did not hold onto her seat.

In the lower house, the winners in all but three seats have been formally declared as counting nears completion.

Prime Minister Scott Morrison is set to govern with 77 seats to Labor's 68, with six MPs on the crossbench - one Green, one Centre Alliance, Bob Katter and three independents.

Australian Associated Press