The household returns and ancillary records for the censuses of Ireland of 1901 and 1911, which are in the custody of the National Archives of Ireland, represent an extremely valuable part of the Irish national heritage. Irish census information is available beginning with the year 1813. After 1821, the census was taken every ten years for the remainder of the nineteenth century. Information for years prior to 1901 are incomplete, as returns from many areas have not survived.
Census substitutes include: