This collection is a subgroup (former Division) of the Montana Department of Revenue records, RS 504. As of 2025, this Division(s) is defunct. The Office of Investigation (formerly the Investigation Division) was abolished in the 1990s. Current legal responsibilities fall under DOR's Legal Services Office, which operates within the Director's Office. Please see the primary finding aid for more Montana Department of Revenue records.

This collection consists of two subgroups: the Investigation Division and the Legal Division. The Investigation Division subgroup is made up of nine series: general correspondence, interoffice correspondence, minutes, news releases, organization, printed materials, reports, subject files, and miscellany. The general correspondence (1973-1980) is arranged alphabetically by correspondent and subject. The folders entitled "miscellaneous" include memoranda and outgoing correspondence primarily of investigators pursuing liquor licensing and child care cases. These folders also include some investigators' reports, some reports regarding liquor licensing and child support, and memoranda concerning Division policies and procedures. The reports series (1973-1981) includes two folders of "activity reports" which are monthly, quarterly, semiannual, and annual reports. These are wholly statistical except for the semiannual and annual reports which contain prose descriptions. The Legal Division subgroup is made up of one series; subject files. The files consist of material compiled as a result of the Department of Revenue's proposal of changes in the Administrative Rules of Montana including the minutes and testimony of hearings, correspondence, proposed legislation, and notes. These files concern, for example, assessment of mining equipment, tax on cigarettes, legal procedures of wine distribution, and coal taxation.