The 2018 census can be filled out online and for the first time, residents will be asked if their house is mouldy.

Letters are due to arrive in households from February 23 for the country's 34th census, which takes a snapshot of the people of New Zealand and the places we live for Statistics NZ.

The most recent census was in 2013 and the 2018 version will be run differently, says the census general manager Denise McGregor.

"This time, we're encouraging as many people as possible to take part online, on or before census day, which is Tuesday, March 6," she said.

"Instead of a census collector delivering paper forms before census day, and then returning to collect them after the day, we're sending all households an access code letter. It contains all the information a household needs to take part in the census online."

The access code can be used by everyone in a household.

Paper forms will still be available for those who prefer them.

For the first time, Stats NZ is asking everyone in New Zealand if their homes are damp or mouldy. This new topic, announced in mid-2017, will add to the picture of the state of homes around the country, Ms McGregor said.

Despite pressure to, Stats NZ decided to leave questions over sex, gender and sexuality out of the census.

- NZ Newswire