People who do not fill out their census forms by tomorrow night will face hefty fines.
The warning comes after 1.4 million households received the questionnaires. Collections will begin all over the country on Monday.
The forms were due to be completed last year but the census was cancelled due to the foot-and-mouth disease.
It is mandatory by law to complete the documents. Failure to do so can lead to a €25,000 fine.
The information collected by the census office will help planning and decision-making in the future.