At the 2013 federal election, more than 1.2 million eligible voters were missing from the electoral roll.

Figures from the Australian Electoral Commission (AEC) at the end of last month show more than 94 per cent of eligible Australians were enrolled to vote in this poll.

But that means about 955,000 people were not enrolled to vote.

The 18 to 24-year-old demographic has the worst numbers on voter enrolment.

Nearly half of all 18-year-olds, and a total of nearly 350,000 young people, are not enrolled to vote.

As the election campaign has progressed, it is expected those figures have climbed, though more recent data is not yet available.

But as the close of the electoral roll draws near, advocacy groups have urged young people to make sure their voice can be heard.

A campaign video from activist group GetUp! Australia encourages parents and grandparents to make sure young people are enrolled.

GetUp's national director Paul Oosting said the main reason young people were under-represented was because they had not voted before.

"They're most at risk of not being on the roll this election," he said.

"This election more than ever will be decided by a small number of votes.

"The youth are really crucial. But to have their voice heard they need to show up, and to be able to show up, they need to make sure they're on the roll by [Monday] afternoon."

Youth vote has the potential to change the course of election

Leo Fieldgrass, from the Australian Youth Affairs Coalition, said young people were politically involved.

"They're focused around individual causes or individual concerns rather than being tied to political parties," he said.

"The real question then becomes what has failed with our democratic system so that we have so many missing voters?"

Mr Fieldgrass said young people, who may move houses more regularly, can get lost in the system, and the enrolment process was too difficult.

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He said it was important politicians did not ignore young people in the election campaign.

"The interesting thing is that there are enough young people out there, enough young voters out there that if they were all enrolled then they could swing an election," Mr Fieldgrass said.

"So I find it incredible that political parties aren't more focused on trying to win over the youth vote."

He said it was also important that young Australians did not miss their chance to hold politicians to account.

"We're at a point in Australia's history where today's young people look set to be the first generation who will have a lower standard of living than their parents," Mr Fieldgrass said.

"We have leading economists warning that young people are getting screwed by our economy."