Charles William Henry Smit, son of Nicholas Hendrick (or Henry) Smit and his wife Mary Ann Sargeant, entered the civil service of the Cape Colony on 1 October 1890 as a practical assistant in the Department of Agriculture, at the Agricultural School, Somerset East. In September 1898 he became a clerk in the Statistical Branch of the Colonial Secretary's Department, and from May 1902 in the Department of Public Health and Local Government. After the formation of the Union of South Africa in 1910 he was appointed on 1 April 1912 as senior clerk and assistant registrar of births and deaths (Cape Province) in the Department of the Interior. By 1917 he was the registrar of births and deaths for the Cape Province and in 1924 was appointed registrar of births, marriages and deaths for all four provinces (with C.J. Boezaart). He was married to Iza Dickon.
Smit's only known contribution to science was a paper entitled 'Notes on the feeding habits of a ladybird larvae' presented at the annual congress of the South African Association for the Advancement of Science, held in Pietermaritzburg in 1916, and published in the annual Report of the association.