As a genre the London chronicles share a number of features of form and structure. However, as the London chronicles were not primarily formal or official documents, there are also many variations in their construction and contents. The following is an attempt to identify and list those features which are common to all London chronicles, and those which appear in most or some of the manuscripts.
The primary identification of a text as a London chronicle depends upon its use of the mayoral list as a means of dating.
All London chronicles name the mayor and sheriffs for the year, with the exception of MS Cotton Vespasian A. XXV which records only the mayors' names.
All London chronicles date according to the mayoral year (October―October).
Variations: The list of mayors and sheriffs is not the same across all the manuscripts; there are many variations in the names presented. Most of these variations are the result of copying errors where names have been accidentally repeated or deleted, or where contractions have been inaccurately expanded. Some manuscripts, however, are clearly working from different lists, where there is a variation in names which cannot be accounted for by scribal error. In a few chronicles the use of the mayoral list as the primary system for dating has been corrupted. In these texts the name of the mayor and sheriffs only appears when there is an accompanying entry.
Some London chronicles include extra information in the mayoral list, such as the name of the guild or company to which the mayor and/or sheriffs belonged. In some cases this is written in the original hand, but it may also be added by a different, sometimes later, hand.
Almost all London chronicles also date by regnal years. This date usually appears next to the sheriffs' names as, for example, 'Anno viiii' or 'yere xii'. It is also sometimes present in the text of the chronicle, e.g. 'In the nth yere of the reign of King henry'.