Australians aged 16 and over are being asked optional questions about their sexual orientation and gender for the first time in the country's census, after the Labor government reversed an earlier decision to exclude them.

One expert says the survey, to be held on the night of 11 August, could be Australia’s most progressive, with new questions on sexuality and gender. What has changed?

Australians can for the first time reveal their sexual orientation and whether they identify as a gender that is not the one recorded at birth in the country's census on Tuesday.