Participation in a census in the UK is a statutory requirement, and the confidentiality of the information supplied by the public is protected by legislation. In Great Britain, the Census Act 1920 as amended by the Census (Confidentiality) Act 1991, and provisions set out in the Census Regulations, lay down penalties for the unlawful disclosure of information from the Census by anyone involved in taking a census. Separate legislation, the Census (Confidentiality) (Northern Ireland) Order 1991 applies in Northern Ireland.

The confidentiality of personal individual census information is taken very seriously indeed. It is unlawful, for example, for the Census Offices to pass any census information to other Government departments or to any other organisation except for the purposes of the Census Act itself or the Public Records Act 1958. Under the latter legislation, the Lord Chancellor has made an Instrument closing census returns to public inspection for 100 years.

The security and confidentiality of the 2001 Census was a subject of a special review and report, and the three UK Census Offices re-affirmed their commitment in a joint statement accompanying the report of the outcomes of the two independent reviews of physical security of Census data and the measures in place to prevent disclosure of personnal information through the statiscal results. The report on the Reviews of Security and Confidentiality was published on 23 March 2001.