The years under which the mayors and sheriffs are listed are basically (with some fluctuations in some early years) the years of the normal term of office, throughout most of this period, of a mayor and of a sheriff: 28/29 October–28/29 October for a mayor, 28 September–28 September for a sheriff. The mayor assumed office in the city on 28 October, but was not fully mayor until sworn before the king or the king's representatives on (at first) 28 or (later; from before 1300) 29 October. See A. B. Beaven, The Aldermen of The City of London (1908–13), II.xxviii and Liber Albus, ed. and trans. H. T. Riley (1861), pp. 18–23; also fitz-Thedmar’s Chronicles of the Mayors and Sheriffs of London, A. D. 11188 to A. D. 1274, ed. and trans. H. T. Riley (1863), pp. 12, 21, 74. For the sheriffs’ 28 September date of assumption of office, see Liber Albus pp. 39–40. Beaven also provides, II.xxviii and xxxiii, the changing dates of the mayor’s and sheriffs’ elections during this period. The sheriffs did not have to be presented to the king or his representatives before their term of office formally began: see also Walter de Gray Birch, ed., The Historical Charters and Constitutional Documents of the City of London (1887), pp. 16, 21, 56. Election and initial oath-taking for both mayors and sheriffs was at Guildhall; subsequently mayors also swore an oath, and sheriffs were presented, at Westminster, or occasionally at the Tower of London. Dates are provided in the database, where available, for elections etc. of mayors and sheriffs who replaced others who died in office or were removed from office, as these occurrences were at non-standard times.
Dates of the death of a mayor or sheriff in office, and the election etc. of a replacement mayor or sheriff, are taken from Beaven where he provides them, and otherwise from the city's manuscript Letter Books, Journals, and Repertories, or other primary or secondary sources, in that order of priority; only the first source in that order is cited, unless primary sources disagree. Where more than one source is provided, without disagreement having been noted, this is because the combination of sources is required for the full information here given. For the period before 1275, various kinds of information are also supplied (and so noted) from Chronicles of the Mayors and Sheriffs of London.