A Short Guide to Act References
Post Office Act 1835 - 5 & 6 Will 4 c.25
In earlier eras, Acts were generally not referred to by anything as straightforward as a name or calendar date. When referred to in subsequent legislation, and sometimes elsewhere, the full title or "long title" as stated at the beginning of the Act was used. These titles could sometimes be several lines long, especially where the Act served a number of purposes – e.g. "An Act to repeal the Exemption from Toll granted for or in respect of Carriages with more than Two Wheels, carrying the Mail in Scotland; and for granting a Rate for Postage, as an Indemnity for the Loss which may arise to the Revenue of the Post Office from the Payment of such Tolls" – and are quoted here where we have a record of them.
However, the more usual method was an abbreviated reference of the form (e.g.) "53 Geo 3 c.68". This denotes the "chapter" of the Act (capita in Latin, usually abbreviated "cap" or "c."), i.e. the consecutive number of those passed in a particular session of Parliament. The sessions themselves are referenced by the regnal year of the currently reigning monarch, not the calendar year. Regnal years commence from the date of accession of the monarch, so contain parts of two calendar years.
Thus the aforementioned "53 Geo 3 c.68" was the sixty-eighth Act passed in the session of Parliament that took place during the fifty-third year of the reign of George III. Sometimes a session would cross more than one regnal year – so "5 & 6 Will 4 c.25" was the 25th Act passed in the session of Parliament that took place in parts of the fifth and sixth years of the reign of William IV. These abbreviated forms are specified in the list of Acts given here.
The modern convention is to abbreviate the name of the monarch using their English name, represent the chapter as "c.", and to use Arabic numerals throughout. Formerly Latinised forms of the names were often used, and uppercase Roman numerals (the latter are still often seen). So for example "5 & 6 Will 4 c.25" (illustrated above) may be seen referred to as "5 & 6 Gul. IV cap.XXV" and intermediate variants (Gulielmi for William).
Occasionally there was more than one session within a regnal year, in which case the chapter numbers ran from 1 for each session and it is necessary to include the session as well, abbreviated "session", "st", or "s." – an example of this would be "24 Geo 3 s.2 c.8".
However, given the complications of the above you may be glad to know that beginning from the 1840s, Acts have generally been given a "short title" to be used as a form of standard citation that is shorter than the full title and clearer than the regnal year reference. Most earlier Acts have been given short titles retrospectively by statute, and they are listed with these in the official Chronological Table of the Statutes published by the Stationery Office. These are used here where available and known. They consist of a few words and the calendar year, e.g. "53 Geo 3 c.68" is the "Postage, etc. Act 1813".
Unfortunately, the same titles have been used more than once for a number of older Acts – e.g. there are three separate Acts listed as the "Postage Act 1825". In the lists here, the chapter number is given after the name when this is this case – this is purely in order to note the situation for the avoidance of confusion, and is not part of the official name of the Act. Occasionally, the stated short title clearly seems to be wrong with reference to the scope of the Act – where this happens, a note has been added.
Since 1 January 1963, this has been further simplified and chapter numbers in each series are numbered simply by the calendar year. The first Public General Act to be passed in a year is "c.1", the second "c.2", and so on. So the "Post Office Act 1969" is simply "1969 c.48", the 48th Act passed that year.
The above refers to "Public General Acts". There are separate sequences of numbers for "Local Acts", typically used for such things as the construction of new buildings, railways etc, or for rules relating to particular local government bodies. These are referred to using lowercase Roman numerals – so for example the "Post Office (Sites) Act 1903" is "3 Edw 7 c.clvi".