That follows a High Court decision on a challenge mounted by left-leaning lobby group GetUp to changes to electoral law that reduced the period in which new voters could enrol.
The AEC said Governor-General Quentin Bryce issued a proclamation on Friday allowing the Electoral Commissioner to update the previously issued lists of voters.
That will be done by printing supplementary voter lists for distribution to polling places. As well letters notifying all affected people of their enrolment status and voting arrangements will be sent from Monday.
In the decision on August 6, the High Court overturned amendments introduced by the Howard government in 2006 tightening the electoral enrolment requirements for new and existing voters.
The tighter rules meant new voters – mostly those had just turned 18 – had to be enrolled by 8pm on the day the election writs were issued, instead of seven days.
The High Court decision has allowed around 100,000 voters who submitted correctly completed enrolment applications by 8pm on July 26 to vote on August 21, the AEC said.
The AEC acknowledged that not all newcomers might find themselves on the roll come election day purely because of the logistics involved in updating the rolls across the country.
In those cases, they can lodge a provisional vote and their details can be checked off later against the electoral roll.
GetUp had a second victory on Friday with the Federal Court opening the way for online enrolment in future elections.
The court said 19-year-old first-time voter Sophie Gravid should be put on the electoral roll after she used GetUp’s website to register her enrolment.
The AEC said Ms Gravid, who signed her enrolment form with a digital pen on a track pad rather than with pen on paper, was now enrolled and could vote.
It said it would need to discuss the decision with the Electoral Council of Australia, a body that includes the Electoral Commissioner and state electoral commissions, to ensure this methodology was appropriate for enrolment across three tiers of government.
“The AEC also will discuss the judgment and associated roll issues with the Joint Standing Committee on Electoral Matters in the next parliament,” it said in a statement.