This article explains the citation of United Kingdom legislation, including the systems used for legislation passed by devolved parliaments and assemblies, for secondary legislation, and for prerogative instruments. This subject is relatively complex both due to the different sources of legislation in the United Kingdom, and because of the different histories of the constituent countries of the United Kingdom.
Each piece of legislation passed by the Parliament of the United Kingdom ("Westminster") is known as an Act of Parliament.
Each modern Act of Parliament has a title (also known as a "long title") and a short title. A short title provides a convenient name for referring to an individual Act, such as "Jamaica Independence Act 1962". The long title is more comprehensive in scope, providing a sometimes very detailed description of the Act's provisions that is too unwieldy for convenient citation; for example, the long title of the Environmental Protection Act 1990 is around 400 words long.
Acts are today split between three series: Public General Acts, Local Acts, and Personal Acts. Each Act within each series is numbered sequentially with a chapter number. Since 1 January 1963, chapter numbers in each series have been numbered by calendar year. The first Public General Act passed in a year is "c. 1", the second is "c. 2", and so on; the first Local Act of a year is "c. i", the second is "c. ii", and so on; while the first Personal Act of a year is "c. 1", the second is "c. 2", and so on (note the use of italics).
Chapter numbers for Acts passed before 1963 are not by calendar year, but instead by the year(s) of the reign during which the relevant parliamentary session was held; thus the Jamaica Independence Act 1962 is cited as "10 & 11 Eliz. 2 c. 40", meaning the 40th Act passed during the session that started in the 10th year of the reign of Elizabeth II and which finished in the 11th year of that reign. Note that the regnal numeral is in an Arabic rather than a Roman numeral.