Census microdata

Microdata are anonymised individual level records sampled from a single census. They contain a range of individual and household characteristics that can be used to analyse with other variables for different purposes.

Microdata do not contain personal information that could identify any household or individual. We remove the information that might identify a person, such as names, addresses and date of birth. We only create microdata after we have applied statistical disclosure control methods, for example record swapping.

Census 2021 microdata products

Census 2021 microdata will be classified in three ways:

  • public

  • safeguarded

  • secure

Census 2021 microdata files will be similar to those published for the 2011 census. Following user feedback, we also plan to produce two new microdata files. The first is a new safeguarded household microdata file. The second is a new microdata file that will contribute to the University of Minnesota’s Integrated Public-Use Microdata Series (IPUMS) project. This is an international project that brings census microdata together from over 100 countries.

Public-access file

This file will contain a sample of data up to 1% of individuals, provided down to a regional level of geography.

Safeguarded individual region file

This file will contain a sample of data up to 5% of individuals, provided down to a regional level of geography.

Safeguarded individual grouped local authority file

This file will contain a sample of data up to 5% of individuals, provided down to a grouped local authority level of geography.

Safeguarded household file – new for Census 2021

This file will contain a sample of data up to 1% of households, provided down to a regional level of geography.

IPUMS file – new for Census 2021

This file will contain a sample of data up to 1% of households, provided down to a regional level of geography.

Secure individual file

This file will contain a sample of data up to 10% of individuals, provided down to a local authority level of geography.

Secure household file

This file will contain a sample of data up to 10% of households, provided down to a local authority level of geography.

Release plans

We plan to make the Census 2021 public access microdata available by March 2023. Due to the complexity of the safeguarded and secure microdata, we plan to make these files available after March 2023. More information will be available in the Census 2021 Outputs Prospectus, to be published early 2022.

Accessing Census 2021 microdata

We will place the most detailed origin-destination data classified as secure, in the ONS Secure Research Service (SRS). It will only be available to approved or accredited researchers.

If you are an approved or accredited researcher, find out how you can access secure research data and what tables you can view.

We are still considering where to place public and safeguarded tables.

Safeguarded data will only be available to data analysts, under certain terms and conditions. The UK Data Service is likely to hold safeguarded data in line with previous censuses.

UK census microdata

We will produce Census 2021 microdata for England and Wales. Where possible this microdata will be harmonised with microdata from Northern Ireland’s census in 2021 and Scotland’s census in 2022.

Working with others

We are working with a range of internal and external individuals and organisations in our microdata working group to design, create, store and disseminate Census 2021 microdata products. We aim to produce Census 2021 microdata products in timely manner that meet our users’ needs as far as possible.

Internal members include topic experts on:

  • migration

  • travel to work

  • demography and census transformation

  • population estimates

  • statistical disclosure control

External members include:

  • National Records of Scotland

  • Northern Ireland Statistics and Research Agency

  • Welsh Government

  • UK Data Service

  • local authorities

  • academia

  • market research

  • commercial research

More information

If you have any questions about Census 2021 microdata products or are interested in joining our working group, please email census.outputs@ons.gov.uk.