A billet is a term for living quarters to which a soldier is assigned to sleep. Historically, it referred to a private dwelling that was required to accept the soldier.
Soldiers are generally billeted in barracks or garrisons when not on combat duty, although in some armies soldiers with families are permitted to maintain a home off-post. Used for a building, the term is more commonly used in British English; United States standard terms are quarters, barracks, "Single (Soldier) Housing" or "Family Housing".
Originally, a "billet" (from the French) was a note, commonly used in the 18th and early 19th centuries as a "billet of invitation." A particular use of the word in this sense is to denote an order issued to a soldier entitling him to quarters with a certain person. From this meaning, the word billet came to be loosely used of the quarters thus obtained. Repeated petitions against the practice of billeting, starting in the 16th century, culminated in its outlawing in 1689 as an extension of a section of the Petition of Right 1628.
During wartime, civilians who have been evacuated from a city in danger of attack are billetted in communal shelters or in the homes of individuals. The practice of billetting evacuees was widespread in Britain during World War II, particularly during the Blitz, when children and other non-essential persons in major cities were sent to rural areas for safety.
In European countries since the formation of regular forces the Quartermaster was an occupation and a rank of the individuals responsible for provision of sleeping quarters as well as other provisions for regular time troops.
One of the major grievances of the American colonists against the British government which led to the American Revolutionary War was the quartering of soldiers in civilian homes. As a result, the Third Amendment to the United States Constitution provides restrictions on the manner in which the Federal government of the United States may require civilians to provide housing for American soldiers.