Notes–bibliography or author–date? Picking your Chicago system

How to tell which one you need

Your module handbook first. If it only says 'Chicago', the discipline is a reliable guide: history and art history use notes–bibliography almost universally; the sciences and quantitative social sciences use author–date.

A quicker test: look at the reading list or a set article. If sources appear as footnotes at the bottom of the page, you want notes–bibliography. If they appear as (Smith 2024) in the text, you want author–date.

Notes–bibliography, formatted

A superscript number in the text points to a note carrying the full citation on first use, then a shortened form afterwards.

First note: 1. Gillie Bolton, <em>Reflective Practice: Writing and Professional Development</em>, 5th ed. (London: SAGE, 2018), 44.

Shortened note: 4. Bolton, <em>Reflective Practice</em>, 51.

Bibliography entry: Bolton, Gillie. <em>Reflective Practice: Writing and Professional Development</em>. 5th ed. London: SAGE, 2018.

Notice the punctuation shift: notes use commas and put publication details in parentheses; the bibliography uses full stops and drops the parentheses. That difference is the most commonly missed detail in Chicago.

Author–date, formatted

In-text: (Bolton 2018, 44). No comma between author and year; a comma before the page.

Reference list: Bolton, Gillie. 2018. <em>Reflective Practice: Writing and Professional Development</em>. 5th ed. London: SAGE.

The year moves forward, directly after the author, and the list is headed 'References' rather than 'Bibliography'.

The differences that matter in practice

• Year position — after the publication details in notes–bibliography, immediately after the author in author–date.
• List heading — 'Bibliography' versus 'References'.
• What the list may contain — a Chicago bibliography may include works consulted but not cited; a reference list may not.
• Discursive space — footnotes let you add commentary that does not fit the argument. Author–date has nowhere to put it, which is a real constraint in historical writing.
• Reader experience — footnotes keep the text clean but push the reader to the bottom of the page. Parenthetical citations interrupt the sentence but keep everything in view.

ibid in Chicago 17

Chicago 17 discourages ibid. The recommendation is to use the shortened note form instead, which is unambiguous and survives editing.

This differs from OSCOLA, where ibid is standard and expected. If you take both law and history modules, that is a genuine source of confusion worth noting.

Converting between them is not a find and replace

Every citation changes position, punctuation and, in notes–bibliography, becomes a note rather than inline text. Converting a 10,000-word dissertation is several hours of careful work with real scope for error.

Decide before you write. If your supervisor is genuinely indifferent, pick notes–bibliography for a source-heavy humanities argument and author–date for anything where the reader needs to see the date of evidence at a glance.