An organized unit of documents grouped together either for current use or in the process of archival arrangement. A file unit is the intellectual grouping of the archival materials, which may or may not equal the physical grouping. For example, a case file may be housed in several physical folders, but described as one file unit.

For example, the file "William D. Beasley and Jean Norris Beasley v. Southern Belle Music, Incorporated et al., Civil Action No. 2390" is one case that makes up the series "Civil Case Files, 1936-1980."