Like many countries, the UK runs a census every ten years.

The census asks each household in the country to provide answers to a series of questions about the individuals living at that address, such as name, age, nationality, languages spoken, education, employment and health.

(More precisely, the census requires answers, rather than requesting them, because participation is mandatory.)

The census happens in any year ending in the digit -1, making 2021 a census year (except in Scotland, where it has been postponed until 2022 due to the coronavirus pandemic).

As you can imagine, most people are answering their 2021 census questions online, with the government sending random but unique 16-character access codes addressed to each known household by snail-mail.

You go to https://www.census.gov.uk/, put in the unique code, and complete the process online – no need to fill in a long paper form by hand and then snail-mail it back.

If you don’t complete the census form (the official closing date was Sunday 2021-03-21), you will receive a series of warning letters, each with a new 16-character code, urging you to get the job done, and reminding you that you could be fined £1000 if you don’t.