Twickenham residents are being asked to spend 10 minutes today filling in the census.

The once-in-a-decade survey determines how many people are living in an area and what the local population needs.

Here are the essentials that you need to know.

What is the census?

The census is a survey of people and households in England and Wales which takes place every 10 years.

It is an official count of every person and household in the country and gives the government the most accurate estimate of who lives where and what they do.

The aim is to build "a detailed snapshot of our society", which helps ministers and councils plan and fund services such as education, doctors' surgeries and roads.

Run by the Office for National Statistics (ONS), the census asks questions about you, your household and your home.

Who needs to complete it?

Every householder at an address is responsible for completing a census questionnaire for their household.

The householder should either answer the individual questions for all household members or make sure each member answers their own.

What sort of questions are included?

Census questions ask about every person living at the property, including their age, race, occupation and relationship status.

For the 2021 census, preparation began several years ago before a white paper was brought to parliament in 2018, followed by a rehearsal the year after.

Background work included user and topic research, testing and evaluation and trying out ideas on people at census events.

Will I get fined if I don't complete it?

Possibly – but you'll be given chances to avoid the penalty.

By law, you must complete or be accounted for in the census.

Census field officers will encourage you to complete it and even help people access any support needed.

It is a crime to provide false information or fail to submit a completed census and those who do so will be contacted by the non-compliance team. If prosecuted, you may have to pay a fine of up to £1,000 plus court costs.

Officers will call on households which have not completed the census after today (Sunday, March 21). But once you've submitted it, you're done!

Do I have to answer every question?

You do not have to answer the questions marked as voluntary.

People staying in the UK for under three months do not have to complete the census, but everyone else should be covered by one – including students and those who have gone abroad for under a year.

[h2]How do I complete the census?

Every household has been sent a 16-digit code to use online to complete the census.

If you can't find your code, click this link to get a code either via text or through the post.

What's different about the census this year?

Residents have been encouraged to complete the form online this year. Paper forms are available by request.

For the first time, there will be voluntary questions on gender identity and on sexual orientation for over-16s.

In the UK, there are no official figures for those who consider their gender as different from their sex registered at birth.

Gathering this information will help develop policy and services and improve equality, the ONS says.

When will the 2021 census details be released?

We'll have to wait until March 2022 to read the initial findings from this year's census, while the final release is a year later in March 2023.

While census data will be used from next year, personal information is confidential for 100 years and by law, cannot be disclosed to any third party before then.