Nearly 100,000 Australians have been added to the electoral roll ahead of the same-sex marriage postal survey - two-thirds of whom are under 25 years old.
The Australian Electoral Commission said on Wednesday it had finished processing more than 933,000 transactions, most of which were to make changes to or update information.
That compares to the 687,000 transactions in the lead up to the 2016 federal election.
More than 98,000 people were added to the roll, of which 65,000 are aged 18 to 24.
That leaves more than 16 million Australians eligible to vote, with data now passed onto the Australian Bureau of Statistics to conduct the marriage survey.
Commissioner Tom Rogers said over 3.3 million visited the AEC website in the two weeks leading up to the close of rolls on August 24.
"With nearly a million transactions received over the past two weeks it is a credit to our staff and systems to have been able to provide completed enrolment data to the ABS early this week," he said in a statement.