There is no official definition of the "home counties". However, the term has been used in legislation and the administration of the armed forces during the twentieth century as follows:
- 1908: The Home Counties Division of the Territorial Force comprised units recruiting in Middlesex, Kent, Surrey and Sussex.
- 1920: The London and Home Counties Electricity District consisted of the counties of London and Middlesex; and parts of Berkshire, Buckinghamshire, Essex, Hertfordshire, Kent and Surrey.
- 1924: The London and Home Counties Traffic Advisory Committee, covering the London Traffic Area: London, Middlesex, and parts of Buckinghamshire, Essex, Hertfordshire, Kent and Surrey.
- 1926: The Home Counties (Music and Dancing) Licensing Act regulated activities in all parts of Buckinghamshire, Essex, Hertfordshire, Kent and Surrey within 20 miles of the City of London or City of Westminster.
- 1938: Green Belt (London and Home Counties) Act limited development in parts of Middlesex, Kent, Buckinghamshire, Surrey, Essex, Berkshire and Hertfordshire.
- 1948: The Home Counties Brigade was formed to administer the infantry regiments of the City and County of London, Kent, Middlesex, Surrey and Sussex.
