The Census of 1880-81 was conducted under the authority of the Census Act (42 Victoria, cap. XXI), which was assented to on 15 May 1879.
The effective date of the census was 04 April 1881. Although enumeration often ran until June, and sometimes later, all information collected was to have been accurate as of the effective date. Children born after this date but before the enumeration were to be excluded, and anyone who died in the same period would still be considered alive for census purposes.
For enumeration purposes, the country was divided into Districts, which as a general rule followed the boundaries of the federal electoral districts, though there were exceptions - cities with multiple Electoral Districts were enumerated as one census District, the Northwest Territories were included as one district despite not being represented in the House of Commons, and parts of Ontario and Manitoba were apparently enumerated as the Districts of Thunder Bay and Keewatin. The Districts were divided into subdistricts, which generally matched the boundaries of municipalities, wards, townships, parishes, and polling districts in developed areas, and rivers and major geographic features in undeveloped areas; many subdistricts were further divided due to size, travel difficulties, or population.
1881 was the first census in which most of Canada was included - British Columbia (1871) and Prince Edward Island both joined confederation after the 1871 Census, while Manitoba and Northwest Territories were considered sufficiently enumerated by their 1870 Census to be excluded in 1871. Part of Labrador was included in Québec, and part possibly in subdivision w of Territories, as Canada recognized the Québec boundary claim at the time. Part of the Northwest Territories were added to Ontario (a - Mattawin, added to District 182 - Algoma) and Manitoba (b through f - renamed and renumbered as District 186½ - Extension); subdistrict b was later awarded to Ontario by the British Privy Council.
The returns consisted of eight schedules, of which only the first schedule was microfilmed; the other schedules were lost, although the statistical information from them did survive and is available in the hardcover reports published by the government. The schedules were:
Because of the near-impossibility of enumerating the Indian population over a large part of the unorganized territory of the country, the aboriginal population was estimated in some subdistricts, specifically "The northern part of sub-district C, of District 187 British Columbia; certain sections of the District in the interior of the same Province; all the sub-districts of District 192 (Territories) with the exception of those included in the Indian Treaties Nos. 1, 2, 3, 4, 5, 6, and 7, with the enumeration of these being made according to the indemnity per head paid by the Department of the Interior; and also with the exception of the principal portion of the Indian population of Eastern Rupert's Land, which has been regularly enumerated." (from the Census report published by the government).