An Australian Bureau of Statistics spokesman said about 16,000 households from Warrnambool and surrounds would test the census for Victoria.

"Warrnambool was selected because the area represents the broader community in Victoria," he said.

Residents will respond to test questions on October 27 and should receive instructions this week or early next week.

"If you don't receive any information, don't worry, there's nothing you need to do," the spokesman said.

The trial involves an Australia-wide sample of 100,000 households and will test whether the census is easy for people to complete, that processes work and that the form captures data accurately.

Unlike the official census, there are no penalties for failing to answer the test questions, however the spokesman said "it's important everyone who is invited participates" to ensure the 2021 census "runs smoothly".

A website crash during the 2016 census locked millions of people out of completing the compulsory national survey. The ABS said for the first time next year people would have a bigger time window to complete the questions, rather than a single night.

"This is all about making it easier for people to complete the form at a time that suits them," the spokesman said.

New questions will also collect data on health conditions and Australian Defence Force service.

"The changes allow the census to collect data on long-term health conditions, such as arthritis and diabetes, to inform health policy and planning for community services," the spokesman said.

"Collecting information about ADF service will provide a better understanding of the circumstances of Australia's veteran community and support better provision of services for this group."

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