Census forms that have been distributed to every household in Donegal are to be filled out tonight.
Every person in the country by law has to be entered on a form.
The census was due to take place last year but was postponed due to the pandemic.
The census is to record people that are staying at a particular address between the hours of 9pm tonight and 7am tomorrow.
The Central Statistics Office has said a number of households may not have received a census yet and if that is the case they can contact the CSO and retrospectively fill a form in the coming days.
Enumerators will return to collect completed census forms starting on 4 April and no later than 6 May.