A 100-strong unit of so-called "non compliance officers" is standing by to visit homes where the census is not filled in.
The enforcers are authorised to conduct interviews under caution and have been given powers to gather evidence against householders who decline to complete the national survey, said a spokesman for the Office for National Statistics (ONS).
Anyone who repeatedly refuses to take part will face criminal prosecution and a fine of up to £1,000.
More than one million people were missed during the last census in 2001, but only 38 were prosecuted.
*** Also if you've not recieved a Census Questionnaire then you MUST request one : http://help.census.gov.uk/england/help/help-and-information/Gettingstarted/Receivingyourquestionnaire/Topics/Notreceivedacensusquestionnaire_H0014A.html