This United States Army regulation, Army Regulation AR 20-1 Assistance, Inspections, Investigations, and Follow up: Inspector General Activities and Procedures March 2020, prescribes policy and procedures concerning the mission and duties of The Inspector General (TIG). It also prescribes duties, missions, standards, and requirements for inspectors general (IGs) throughout the Army. Responsibilities are prescribed for commanders and heads of agencies, activities, centers, and installations for the support of IG activities.This regulation prescribes the responsibility and policy for the selection and duties of inspectors general throughout the Army. It describes inspector general functions, including teaching and training, inspections, assistance, and investigations. Although the fundamental inspector general role and functions have not changed, this revision incorporates numerous policy and mandated procedural changes affecting inspector general activities. This regulation implements DODD 5505.06. This regulation applies to the Regular Army, the Army National Guard/Army National Guard of the United States, and the U.S. Army Reserve, unless otherwise stated. It also applies to Department of the Army Civilian employees and nonappropriated fund employees. During mobilization, the proponent may modify chapters and policies contained in this regulation.