Although from 1801-1831 census data was collected every ten years from residents in the United Kingdom, it was of the statistical kind and it was not until 1841 that a more modern census was introduced where some personal information was asked for.
According to the Enumeration Abstract, England and Wales was divided into Enumeration Districts, the boundaries of which were strictly defined so that it should contain not more than 200, and not less than 25 inhabited houses. In that respect, an active man could travel over between morning and sunset on a summer’s day, and obtain from each person dwelling therein all the particulars required by the Act. Further, to the office of Enumerator, was appointed by the Registrars, one individual for each of these sub-divisions, selected from the neighbourhood, with reference to his particular fitness for the office. In consequence of the small size to which these districts were necessarily limited, no less than 35,000 such persons were required for England and Wales.
Although the information to be gained from the census would help the government in dealing with trends such as rising population and overcrowding, some people may have been suspicious and felt the government were unnecessarily snooping into their affairs and therefore were not honest in their answers. For those, especially the elderly, who had lived under the old poor law act whereby they thought they would be removed back to where they were born if they could not prove a right to settlement, may when asked on the 1841 census if they were born in the county, have said yes. Ten years later when asked for a specific place of birth they may have stated where they currently lived especially if their living conditions were better off than where they were born. Others listed themselves as widowed especially if they had been abandoned by a spouse for another woman, as was the case with an ancestor of mine, or indeed as married if they were living with someone even if they were not legally married.
The 1841 census only allowed people to list one occupation even if they had more than one. On the 1841 census my 4th great grandfather was listed simply as a Labourer however in the census of 1851 he was a Farmer of 33 acres and Labourer. This information appears to make a difference in how the family may have been perceived in socio economic terms. The other aspect of the 1841 census was that no relationships were added so assumptions could be made by family historians that Joe and Mary Bloggs were married but they were actually brother and sister. Unless later documentation is available to prove otherwise these types of assumptions can lead to further errors in family trees. There can also be some ambiguity in information that was listed for relationship in the later censuses where terms were mixed up or plain incorrect. I have one instance where the sister of my 2nd great grandmother was living with her and my 2nd great grandfather but instead of sister or sister-in-law she is listed as servant. It was only through searching other records that the servant was discovered to be the sister who was 13 years younger.
The 1841 census occurred in Summer on Sunday 6 June and was a harvest night therefore there were potentially many people involved in agricultural work that were missing from the census including farming servants and labourers in husbandry. A count of seaman working offshore was given but no individual details and members of the armed forces outside of the UK were also not included. This in effect means that for many family historians details of people as close as 2nd or 3rd great grandparents are not going to be found in census records which in some cases means any further research in a family line may be halted.
With the first new census householders were meant to receive written instructions on how to complete the form. This in itself would not be helpful if the householders were illiterate and apparently in practice not many guidelines were given to households. For those that required help either through being confused regarding aspects such as whether lodgers, servants and boarders should be included or where they were illiterate, when the enumerator returned to collect the form they would help to fill it in. This did not mean that all information written down by the enumerator was correct either as householders may have been unsure on how old they really were or the enumerator may have rounded up or down the age for anyone over 15, they may have used derivatives of names, nicknames or middle names and surnames may have been written phonetically if an unusual name. My surname Haigh could have been miswritten by an enumerator as Haig, Hague or Hay for example. I have an ancestor named Henry who was listed on the census as Hal, a great grandparent who was called John Thomas and his wife Mary Jane yet he was listed as Thomas John and she correct as Mary Jane. My 2nd great grandparent, Mary Jane Sharp was aged 2 in the 1851 census, 28 in 1881, 39 in 1891, 44 in 1901, 57 in 1911 and died in 1922 aged 73. In the later censuses Mary Jane was therefore +11 years, +5 years, +13 years. The various census records also had her name as Mary Jane, Jane and Mary Ann.
In the 1841 census the Y or N question for whether born in the district could also be incorrect if people were living close to a border or the handwriting of the enumerator could be interpreted incorrectly as the Y and N look similar. For the 1851 census where place of birth was asked for sometimes a main place might have been listed such as Yorkshire as opposed to drilling down to Wakefield or just a house or farm name was given. There have been instances where place names that don’t even exist have been written on early census records as the birth place of an ancestor and it is only through establishing families in later censuses that a potentially true birth place be established. If an enumerator from London was sent to a district like Newcastle or Liverpool where residents had very broad accents this could account for misinterpretation of names and place names. Unfamiliarity of districts could also account for whole streets being missed by the enumerator.
The census images that are available to view were written by enumerators into books therefore are transcripts of the original household census forms collected and consequently also provide opportunity for errors to be created particularly if deciphering handwriting by those barely literate. The accuracy of the answers to questions could also be queried depending on the householders level of literacy. Unfortunately the 1841 census was also recorded in pencil and thus parts of it have faded however through digital technology this has been somewhat abated with the ability to zoom into scanned documents.
Not all of the 1841 census records have survived and some of the 1851 records are also missing. The records of 14 parishes in Fife, Scotland were lost when the ferryboat carrying them sank enroute to Edinburgh. A handful of original 1841 census returns in London have also lost. Websites such as Ancestry and Find My Past have long lists of missing parishes from the counties of Cheshire, Derbyshire, Hampshire, Kent, Middlesex, Northamptonshire, Oxfordshire, Somerset, Surrey, Wiltshire and Yorkshire.
It would be very rare for census records to ever be fully complete or accurate particularly with the 1841 census being something completely new for the people of England and Wales. The fact that this census was taken in Summer meant that there is no inkling as to how many people were actually missing due to employment or those who had no fixed address for example but it was something the Government were concerned with. A significant change for the 1851 and future censuses was to bring the census date forward to Spring with the 1851 census taking place on Sunday 30 March. The other consideration regarding accuracy is that not only were errors potentially made initially by enumerators but modern transcribers do not always get the information correct either. I recall searching for an ancestor that has been eluding me for years and thought I’d struck gold when I found a transcription for the exact unusual name I had put in only to open the document and find the transcriber had used two peoples names within the document that formed the exact name I was looking for. It is always worth checking transcriptions from various websites but also the original document in order to gain some sort of clarity surrounding records. Finally never take for granted information that other people may have placed in their trees from census records without verifying it actually belongs to your ancestor or is indeed transcribed correctly, it is not only people in the past that can misinterpret information.
 Enumeration Abstract, https://www.visionofbritain.org.uk/census/GB1841ABS_1/2.  Jolly, Emma, Tracing Your Ancestors Using The Census, Pen & Sword, 2019 ed., pp46, 48.  Jolly, Emma, Tracing Your Ancestors, p48