In the 7th century, Dál Riata (parts of what is now Scotland and Northern Ireland) was the first territory in what is now the UK to conduct a census, with what was called the "Tradition of the Men of Alba" (Senchus fer n-Alban). England took its first Census when the Domesday Book was compiled in 1086 for tax purposes.
The UK census as we know it today started in 1801 (championed by John Rickman who managed the first four up to 1831), partly to ascertain the number of men able to fight in the Napoleonic wars, partly over concerns stemming from An Essay on the Principle of Population by Reverend Thomas Robert Malthus (1798). Rickman's 12 reasons - set out in 1798 and repeated in Parliamentary debates - for conducting a UK census included the following justifications:
The census has been conducted every ten years since 1801 and most recently in 2001 (see United Kingdom Census 2001). The first four censuses (1801-1831) were mainly statistical. That is, they were mainly headcounts and contained virtually no personal information; a very small number of older records exist in local record offices as by-products of the notes made by enumerators in the production of those earlier censuses, these might list all persons or just the heads of households. The 1841 Census was the first to intentionally record names of all individuals in a household or institution;
Because of World War II, there was no census in 1941. However, following the passage into law (on 5 September 1939) of the National Registration Act 1939 a population count was carried out on 29 September 1939, which was, in effect, a census.
Although the 1931 census was taken on 26th April 1931 the returns were destroyed by fire (in an accident and not after bombing) during the Second World War.
However, the 1901 and 1911 censuses for Northern Ireland have been available for inspection since 1960 and the 19th century Scottish censuses were all released after 50-80 years of closure. In exceptional circumstances the Registrar General for England and Wales does release specific information from 70-, 80-, or 90-year old closed censuses (including the 1911 census).
It has been argued that in England and Wales no attempts were made by ministers and civil servants strictly to enforce the 100-year census closure policy until 2005, five years after the Freedom of Information Act 2000 was passed, which some have argued abolished the 100-year rule. However, personal information provided in confidence is clearly exempted if its disclosure could result in a successful prosecution for breach of confidence. The 1911 Census is now partially accessible following a decision by the Information Commissioner's Office. A March 2007 internet petition to reduce the classified period for census data from 100 years to 70 years received a response from the government explaining why this was not possible.
In January 2002, the much-anticipated England & Wales census for 1901 went online. Within minutes it was inaccessible because of server and network load, and it had to be taken offline. Later in the year, after upgrades had been made, it came back online.
Controversially, the Northern Ireland census included a supplementary question on what religion a person was brought up in for those stating no religion in response to the main question.
See also: Demographics of England from the 2001 United Kingdom census
| Year | Date | Notes | New questions asked |
|---|---|---|---|
| 1801 | 10 March | Details collected were mainly head-counts, with few still existing. | |
| 1811 | 27 May | Details collected were mainly head-counts, with few still existing. | |
| 1821 | 28 May | Details collected were mainly head-counts, with few still existing. | |
| 1831 | 30 May | Details collected were mainly head-counts, with few still existing. | |
| 1841 | 6 June | Name. Age (For those over 15, this was rounded down to the nearest 5 years). Occupation. Whether born "in county" or not. | |
| 1851 | 30 March | Relation to head of the household. Marital status. Place of birth. Whether blind, deaf or dumb. | |
| 1861 | 7 April | ||
| 1871 | 2 April | Whether an imbecile, idiot or lunatic. | |
| 1881 | 3 April | ||
| 1891 | 5 April | Whether an employer, an employee, or neither. Number of rooms occupied, if less than 5. | |
| 1901 | 31 March | Whether an employer, worker or working on one's own account. Whether working at home or not. | |
| 1911 | 2 April | How long the couple has been married. How many children were born alive, how many who are still alive, and how many who have died. Industry or service with which the worker is connected. | |
| 1921 | 19 June | ||
| 1931 | 26 April | Destroyed in World War II | |
| 1939 | 29 September | National Registration Act 1939. No census in 1941 because of the Second World War. | |
| 1951 | 8 April | ||
| 1961 | 23 April | ||
| 1971 | 25 April | ||
| 1981 | 5 April | ||
| 1991 | 21 April | ||
| 2001 | 29 April | ||
| 2011 | 27 March |