Census Day was Sunday 21st March 2021.
However there is still time to take part in the census.

You should have received a letter with a household access code.
The census takes about ten minutes per person in your household to complete at http://www.census.gov.uk
If you need help filling out the form you can call the Contact Centre on 0800 141 2021
If you need to speak to someone in another language (other than English), call the free language helpline on 0800 587 2021