Duty officer is the name of a rotating position assigned to a junior military officer in a duty or watch system. The duty officer is charged with responsibility for a military unit and acts as the commanding officer's representative. The duty officer attends to menial tasks for the commanding officer such as being at the scene of an incident and being on call during the night. This duty is in addition to the officer's normal duties.
The duty officer's tour is generally 24 or 48 hours, after which he will be relieved by the oncoming duty officer listed on the roster or watchbill. The offgoing duty officer will turn over relevant data and documentation to his relief about the previous day's happenings, before returning to his normal duties (or going on liberty if his duty ends on a weekend or other non-work day).
In the Indian Army, the duty officer is in charge of maintaining discipline and order in an Indian Army Unit. He is also in charge of the guards on duty, and conducting inspections of the quarter guard at any time of day or night. A duty officer also has a duty JCO and a duty NCO to assist him in discharging his duties. The duty JCO and duty NCO would be wearing a brassard or an arm band with the words "duty JCO" and "duty NCO" marked on them.
In the United States armed forces, the duty officer is generally in charge of a unit headquarters in the absence of the commander. His duties include inspection of soldiers on guard duty (also called watchstanders in the Navy), being in charge of quarters at the company and battery level and staff duty NCOs at the battalion level, inspection of the arms rooms, motor pool and unit dining facilities. The duty officer will contact the commander and senior NCOs if emergency messages are sent to the unit. The duty officer usually carries a notebook and briefcase with a series of phone lists and checklists put together by the unit adjutant to guide the officer through his tour of duty.
In the Finnish armed forces, the duty officer (päivystäjä in Finnish), usually a conscript NCO, is responsible for maintaining the order in the unit, monitoring persons entering and leaving it and keeping count of its weapons. His tour is 24 hours long and he has two assisting officers, usually privates, who relieve him during lunch, dinner, a recreation break and during the night. The duty officer is stationed behind a desk at the unit's main entrance which should be manned at all times.
In various navies, a similar position called the "officer of the Day" or "officer of the deck" (OOD) also exists. Some commands have both an OOD and a duty officer simultaneously with a delineation in duties while in others only one exists.
Station duty officer is a public position in a union, who handles non-emergency calls and other clerical duties for front officers.