Everyone in England, Wales and Northern Ireland has to fill in the Census this Sunday, or risk getting a £1,000 fine.
Millions of people were sent letters this month with a unique code to enable them to fill in their Census online.
But some people have reported that they never received a letter, while others have mislaid theirs.
Filling in the Census is a legal obligation, with a £1,000 fine if you don't fill it in, and thankfully there is a way to get a new code if you've lost your original.
You can get a new code from the Census Website, by following the instructions here.
The Census website said: "You can request a new access code to start a new census if you have lost or not received an access code. This can be sent to you by text or post.
"A new access code will start a new census, and you will lose any answers entered using a previous access code.
"You can also request a paper census questionnaire to be sent in the post."
The census is a survey that happens every 10 years and gives a picture of all the people and households in England and Wales.
Your answers to the census questions will help organisations make decisions on planning and funding public services in your area, including transport, education and healthcare.
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After Census Day, at the end of March and into April, census field officers will be visiting households that have not filled in the form.
They will encourage people to complete the census and help you to access further help if you need it. The field officers will never need to enter your house.
The field officers will be working in the same way as a postal or food delivery visit. They will be wearing Personal Protective Equipment (PPE) and working in line with government guidance.
