More than 1.3 million Australians still aren't enrolled to vote in the federal election.
And with Monday night the deadline, the Australian Electoral Commission (AEC) faces an uphill battle to persuade around five per cent of the nation to register.
About 100,000 people have enrolled since June, thanks in part to a high profile advertising campaign, links posted on Facebook and Twitter and a new online enrolment system.
The AEC expects a late flurry this weekend but a spokesman conceded there will be some who miss the 8pm (AEST) Monday deadline and won't be eligible to vote.
"This position we're in this election is already better than the position we were in during the 2010 election," AEC spokesman Evan Ekin-Smyth told AAP on Friday.
"There was overall 1.5 million people missing from the electoral roll when the 2010 election occurred.
"So being at 1.3 (million), given population rises and factors like that, we're much better off."
The AEC plans another promotional blitz this weekend, including TV and social media adverts.
At least 40,000 people have clicked through to the AEC enrolment web page from links posted on Facebook.
The AEC's shareable enrolment links were designed to encourage about half a million people aged between 18 and 24 who were not registered to vote in June.
Similar links were posted on Twitter.
This election is the first that Australians have been able to enrol for online, or update enrolment details.
Mr Ekin-Smyth said up to 65,000 people have been enrolling or changing address details each day this week.
