Ti Butler, 27, from Melbourne's north east will tick the "other" box.
"I have days when I identify as a boy, I have days when I identify as a girl," Ti said.
"Some days I'm in between, some days I'm a bit of both, some days I'm neither. It changes, it's quite difficult to keep track of sometimes."
The default question in the Census asks whether you're male or female.
But, if these responses don't apply to you, the ABS says it has special procedures in place.
The paper form requires the male and female boxes to be left unmarked, and your response written in.
Responding online however requires the following extra steps:
Call the Census Inquiry Service, request a login for the special online form and then select "other" when completing the question.
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Sue Taylor is the 2016 Census Data Director with the Australian Bureau of Statistics.
"It's in recognition of that fact that sex and indeed gender are no longer seen as purely binary options for response," she said.
"Community expectations are such that we really need to start thinking about how we are going to enable people to report as they would like to."
The Bureau said it's conducted consultations with members of the LGBTI communities.
That's something Rowena Allen, Victoria's Gender and Sexuality Commissioner, was involved with years ago.
"For me, it's been a 10-year journey and I know there've been a lot of advocates. Last time we were told - this is five years ago, or even ten years ago - that it wasn't doable, that it would be too expensive to do," she said.
The research also went global.
"We are in contact of course with other census agencies across the world and a lot are grappling with the same issue of how best to ask this type of question," Ms Taylor said.
And now, 105 years since the first census, Rowena Allen welcomed the "other" option.
"I think it's fantastic because it's a free box. So if we had to tick something we would never get enough boxes. People identify their gender and sexuality in a whole lot of ways."
Ti Butler says it's a platform for people who have struggled to be heard.
"I think it's good we getting recognised finally. We've been here for a very long time but we've not had the data to be able to say that."
The ABS is urging respondents to help provide an accurate snapshot of Australia's rapidly growing and changing population.
