What is the Census and do I have to complete it?

A snapshot of life across most of the UK will be captured on Sunday as millions of people complete the 2021 Census.

The once-in-a-decade event will take place in England, Wales and Northern Ireland, with households answering questions about their health, education, employment status and more.

Here we break down what it is all about:

What is the Census?

The Census is essentially a head count of everyone in the country on a given day. This year that date is Sunday March 21.

Households are provided with a detailed questionnaire asking a host of questions about those who live there.

The huge survey has been taking place every 10 years since 1801 (except in 1941), with the last one being in 2011.

The Census is run by the Office for National Statistics (ONS) in England and Wales and by the Northern Ireland Statistics and Research Agency. Scotland’s Census has been delayed until March 2022 due to the coronavirus pandemic.

The Covid outbreak also means the Census in England, Wales and Northern Ireland will be the first to be primarily completed online.

What information does the Census ask for?

The Census questions ask for details on people’s sex, age, ethnicity and the status of their health, education and occupation.

There are also questions on your main language, national identity and marital status.

Some questions, such as those on sexual orientation, gender identity and religion, are optional - it is the first time that sexual orientation and gender identity will be recorded by the census.

Officials say it takes about 10 minutes to complete.

Why do they need these details?

Peter Benton, director of population and public policy operations at the ONS, told the BBC that the Census is the “fundamental bedrock of our statistical system”.

Organisations such as local authorities and charities use the information it gathers to build a picture of what services communities might need, such as around transport, education and healthcare.

For example it could inform the planning and funding around doctors’ surgeries, housing or bus routes.

When does the Census have to be completed?

Census day is Sunday March 21 and households should provide information about themselves as it stands on that date.

Households should have already received letters containing an access code to log in and complete the form online via a computer, smartphone or tablet.

Paper questionnaires can also be requested to be sent in the post.

The Census should be completed on Census day itself or as soon as possible afterwards.

You can fill out the form early, as long as you are confident the details will not have changed by Census day.

Do you have to fill in the form?

Yes, by law you must complete the Census. Failure to do so risks prosecution and a fine of up to £1,000.

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

They can answer the individual questions for all household members or make sure each member fills in their own.

The Census includes students, people with no fixed address and those living in canal boats, care homes, refuges or serving in the armed forces.

People staying in the UK for less than three months are not responsible for filling in the Census.

What happens after Census day?

At the end of March and into April, Census field officers will visit households which have not submitted a completed Census form to encourage them to do so.

The ONS said officers will never need to enter a house, will be wearing personal protective equipment (PPE) and will work in line with Government guidance.

Will my data be private?

The ONS said personal information on a Census is only used for statistical purposes and it will never sell or share personal information with anyone.

Mr Benton told the BBC: “The Census data is confidential.

“We don’t pass it to Government, to the local authorities, to the immigration authorities; it stays locked away for 100 years – apart from the aggregate statistics that we produce.

“If I were in the office now, underneath my desk we have a basement, and that has all of the 1921 forms in it, and they’re currently being scanned and digitised so that in 2022, 100 years later they’ll finally see the light of day.”

What is the history of the Census?

Mr Benton explained that, at the time of the first census in 1801, when there were around nine million people in England and Wales, the concern was “about whether we would have enough fighting men to fight in the Napoleonic wars”.

He added: “You get to 1921, and there were questions about whether kids are orphaned obviously because of the First World War and the Spanish flu.

“And then the Census keeps moving with the times, so you get to the 50s, and the 1951 census is all about housing – how many people have got a kitchen sink? How many people have only got an outside toilet?

“And then for the next couple of decades that was a focus, but now housing is of a much higher quality and the Census now is looking at all the diversity of the population so our local services can be really well planned.”