The census is scheduled for Wednesday and Thursday, and will provide sorely needed up-to-date demographic data for the country which has an estimated population of around 44 million. It will be the first census to cover all 18 governorates since 1987, when dictator Saddam Hussein was in power, following repeated delays caused by years of war and political tensions between factions.
A count conducted in 1997 excluded the three northern provinces that make up the autonomous Kurdistan region. The upcoming census has reignited tensions between Baghdad and Kurdistan over disputed territories in the north.
The census includes religion but does not differentiate between sects, such as Sunni and Shiite Muslims, and, unlike previous counts, it excludes ethnicity.
Prime Minister Mohammed Shia al-Sudani said the census was important for "development and planning steps in all sectors that contribute to the advancement and progress of Iraq", where electricity is scarce and infrastructure largely in disrepair.
During the census a two-day curfew will operate, with families having to stay at home so 120,000 researchers can collect data directly from households.
Demographics are likely to have shifted with the exile of hundreds of thousands of Christians, and also of tens of thousands of Yazidi families who were displaced from Sinjar by atrocities committed by IS extremists.
To organise the count, authorities partnered with the United Nations Population Fund (UNFPA), in an effort to generate "accurate demographic information, facilitating effective policymaking and promoting inclusive growth".
Previous censuses were cancelled mainly because of tensions over disputed territories between the Kurdish, Arab, and Turkoman communities in the northern governorates of Kirkuk and Nineveh.
In the census, Baghdad has agreed to register only the descendants of families who were present in the disputed territories during the 1957 count, in order to prevent subsequent waves of migration from disrupting the demographic balance. Newcomers will be counted in their province of origin.