The 2011 UK Census website (for England and Wales) includes an FAQ page which covers the question of what will happen if someone fails to complete their Census information. It states that "You could face prosecution, a hefty fine (up to £1000) and a criminal record." Given this, and for the ten minutes of time that it will take to fill in the Census form, it’s probably better to grit your teeth and fill in the details rather than risking the consequences.
Another question that commonly crops up is "what do I do if I’m on holiday when the Census is issued?" The Census website FAQ page also covers this, stating that "You should complete your questionnaire as soon as possible after 27 March 2011. Or do it before you go away if you've already received your questionnaire. If everyone in the household is away on census day you should complete your questionnaire as soon as possible after your return. If the household is absent for more than six months after census day, you do not need to complete the questionnaire. Anyone away from home for up to 12 months should still be included on your questionnaire." It sounds therefore as if there is a bit of leeway in terms of how quickly you must complete the form to cover instances where people are away on holiday, etc.
There may also be instances where individuals might find it difficult to complete the form. Examples could include where the individual is ill or infirm or where they are illiterate. The Census website explains that help can be sought, through their online help content or by phoning their helpline. The support provided includes a Text Relay for people with hearing impairment. It also states that a carer, friend, or other family member may complete the questionnaire on behalf of an individual if they are unable to do so.
The information that I have sourced for this article was taken from the UK Census website for the jurisdictions of England and Wales. A separate version of the Census is issued both by Scotland and by Northern Ireland but the details of what happens if you fail to complete the questionnaire and the help that’s available should be the same. For further information, I’ve included the Scottish Census website and Northern Irish Census website urls in the "Sources" section below.
England and Wales Census website: http://www.ons.gov.uk/census/i ndex.html
Scotland Census website: http://www.gro-scotland.gov.uk /census/censushm2011/index.htm l
Northern Ireland Census website: http://www.nisranew.nisra.gov. uk/census/start.html