Chicago 18 Citation Guide 2026: Notes and Author-Date

The Chicago Manual of Style (CMOS), 18th edition, is a major citation and editorial reference in history, fine arts, religious studies and other humanities fields. The University of Chicago Press published CMOS 18 in 2024. This guide explains its two citation systems and the checks a thesis writer or graduate student should make before submission.

This is the authoritative practitioner reference, not a marketing summary. All examples are checked against the official Chicago Manual of Style Online (https://www.chicagomanualofstyle.org).

Two Systems: Notes-Bibliography (NB) and Author-Date (AD)

Chicago's defining feature is that it offers two parallel citation systems, each suited to different disciplines. Both are equally official; you pick one and use it consistently.

Notes-Bibliography (NB) is the older, more traditional Chicago system. You insert a superscript number in the text; the corresponding footnote (or endnote) gives the full citation. A bibliography at the end lists all sources alphabetically.

Author-Date (AD) is closer to APA. You cite (Author Year, page) in parentheses; a reference list at the end gives full details. No footnotes for citations (though you can still use footnotes for substantive remarks).

History, art, music, theology and literature programs often choose NB. Programs that use Chicago in business, social sciences or sciences may choose AD. The assigned style guide or your supervisor determines the required system. Do not mix the systems unless your institution explicitly permits a special case.

What Chicago 18 Is, Who Maintains It, and When to Use It

The Chicago Manual of Style is published by the University of Chicago Press and is more than a citation style: it's the leading English-language editorial reference, used by book editors, journal publishers and government style guides worldwide.

Official source: https://www.chicagomanualofstyle.org
Free quick guide: https://www.chicagomanualofstyle.org/help-tools/quick-guide.html
Book: The Chicago Manual of Style, 18th edition (2024), in print or through the official online subscription.

Disciplines that often use Chicago 18 NB:

• History (all subfields)
• Art history, architecture, art studies
• Theology, religious studies, biblical studies
• Musicology, music history, music theory
• Classical studies, ancient history
• Some literature programs (especially comparative literature, world literature)
• Anthropology (some programs)

Disciplines that sometimes use Chicago 18 AD:

• Some business and management programs
• Some social science programs (sociology, anthropology)
• Some sciences (less common; more often IEEE, AMA, Vancouver, or APA)

If you don't know which Chicago system to use, ask your supervisor before writing. Switching mid-thesis is extremely painful.

Turabian: The Thesis Version of Chicago

Kate L. Turabian's A Manual for Writers of Research Papers, Theses, and Dissertations is the student/thesis adaptation of CMOS. It's published by the same press and follows the same rules with simplifications and a focus on student writers.

Current published edition as of August 2026: 9th edition, April 2018. The University of Chicago Press lists the 10th edition for publication in November 2026.

If your university or department specifies Turabian, use the edition it names. Turabian 9 remains the published edition until the announced 10th edition is released, so do not assume that every Chicago 18 change already applies to a Turabian assignment.

Many humanities graduate programs use Turabian for dissertations and CMOS for journal submissions. Check which one your program requires.

Notes-Bibliography System (NB): In-Text and Footnotes

In the NB system, every cited source appears in two places: in a footnote (or endnote) and in the bibliography.

Footnote: full citation on first mention

The first time you cite a source, the footnote gives the full citation.

First footnote (book):

1. Jane Smith, The Reading Mind (New York: Routledge, 2023), 142.

First footnote (journal article):

1. Adam Jones, "Memory Consolidation during Sleep," Sleep Research Journal 12, no. 2 (2022): 45-60, doi:10.NNNN/example

The footnote begins with the author's first name first (not surname-first like in the bibliography). Title in italics for books, in quotation marks for articles. Publication details in parentheses. Specific page reference at the end.

Shortened note: after first citation

After the first full citation, subsequent footnotes for the same source use a shortened form: surname, shortened title, page number.

1. Smith, Reading Mind, 89.
2. Jones, "Memory Consolidation," 50.

Chicago prefers shortened citations to repeated full notes. Follow the current manual and any institutional guide on whether ibid. is permitted rather than treating it as a universal requirement.

Substantive footnotes

Footnotes can also contain substantive material (an aside, a clarification, a discussion of a contested point) in addition to or instead of citations. This is one of Chicago's strengths over APA: the footnote architecture allows for richer commentary without breaking the text flow.

NB Bibliography: General Rules

The bibliography appears at the end under the heading Bibliography, centered, on a new page.

Universal formatting rules:

• Single-spaced within an entry, double-spaced between entries (Chicago default; many universities prefer double throughout)
• Hanging indent of 0.5"
• Alphabetical order by first author's surname
• Author names: surname first for the first author, then "First Name Last Name" for additional authors
• Up to 3 authors listed in full; 4+ uses first author + "et al." in footnotes but lists all in the bibliography (up to 10; for 11+, list first 7 + et al.)
• URLs included as direct links; DOI preferred when available

Author names

First author: Surname, First Name. Second/subsequent authors: First Name Last Name.

Smith, Jane, and Adam Jones.

URLs and DOIs

DOI is preferred when available. If both DOI and URL are available, use the DOI:

doi:10.NNNN/example

Stable URLs included as direct links. Access dates included only for time-sensitive content.

NB Bibliography: Examples by Source Type

Book (single author)

Smith, Jane. The Reading Mind. New York: Routledge, 2023.

Title in italics, title case. Publisher format: location: publisher, year.

Book (two or three authors)

Smith, Jane, and Adam Jones. The Reading Mind. New York: Routledge, 2023.
Smith, Jane, Adam Jones, and Lisa Brown. The Reading Mind. New York: 
Routledge, 2023.

Book (four or more authors)

In the bibliography: list all authors up to 10 (then first 7 + et al. for 11+).

Smith, Jane, Adam Jones, Lisa Brown, and Michael Davis. The Reading Mind. 
New York: Routledge, 2023.

In a footnote: first author + et al. (even for 4 authors).

1. Smith et al., Reading Mind, 142.

Book chapter (edited volume)

Dupuis, Marc. "Chronic Pain Assessment." In Treatise on Pain, edited by 
Raphael Rey, 3rd ed., 234-256. Paris: Maloine, 2021.

Edited book (citing the whole volume)

Rey, Raphael, ed. Treatise on Pain. 3rd ed. Paris: Maloine, 2021.

Journal article

Smith, Jane, and Adam Jones. "Reading Speed and Aging in Monolingual Adults: 
A Longitudinal Study." Journal of Cognitive Aging 45, no. 3 (2023): 234-251. 
doi:10.NNNN/example.

Article title in quotation marks. Journal title in italics. Volume and issue without "vol." or "no." abbreviations (just numbers).

Thesis or dissertation

Garcia, Maria. "Cognitive Reserve and Bilingualism in Aging." PhD diss., 
University of California, Berkeley, 2022. ProQuest (UMI 28412345).

Webpage

World Health Organization. "Mental Health and Well-Being." March 15, 2024. 
https://www.who.int/health-topics/mental-health.

For continuously updated pages, add an access date:

World Health Organization. "COVID-19 Dashboard." Accessed May 19, 2026. 
https://covid19.who.int/.

Newspaper or magazine article

Goldstein, Dana. "Reading Scores Recover Post-Pandemic." The New York Times, 
April 22, 2024. https://www.example.com.

Archival source (one of Chicago's strengths)

Chicago has well-developed conventions for archival sources, which is one reason historians prefer it.

Smith, Jane. Letter to John Doe. May 15, 1923. Smith Family Papers, Box 3, 
Folder 12, Special Collections, University of Chicago Library.

Government document

U.S. Department of Health and Human Services. The State of Mental Health 
in the United States. Report no. NIH-23-MH-001. Washington, DC: U.S. 
Government Publishing Office, 2023. https://www.example.com.

Film

Nolan, Christopher, dir. Oppenheimer. Universal Pictures, 2023. Streaming 
video, 3:00. https://www.netflix.com/title/example.

AI-generated content (CMOS Q&A, 2023-2024 guidance)

Chicago's official Q&A treats AI-generated content as personal communication (cite in footnote, not in bibliography):

1. ChatGPT, response to prompt "Summarize the themes of Hamlet," OpenAI, March 14, 2024, https://www.example.com.

For frequent AI use in a research project, document the prompts and outputs in an appendix. Disclose AI use per your institution's policy.

Tweet / X post

@CMSCBs. "CMOS 17 is the current edition in 2026; CMOS 18 has been announced 
but not yet released." X, March 5, 2024. https://www.example.com.

Author-Date System (AD): In-Text and Reference List

The Author-Date system uses parenthetical in-text citations and a reference list (like APA, but with slightly different formatting).

In-text citation

(Smith 2023, 142)

Note: no comma between author and year, comma before page number. Page is included for direct quotes; recommended for paraphrases.

If the author is named in the sentence, only the year and page are in parentheses:

Smith argues that reading speed declines with age (2023, 142).

Multiple authors

(Smith and Jones 2023, 142)
(Smith, Jones, and Brown 2023, 142)
(Smith et al. 2023, 142) [for 4+ authors]

Multiple sources

(Smith 2023, 142; Jones and Brown 2022, 89)

Reference list entries

Reference list entries differ from NB bibliography mainly in: date placement (right after author, in parentheses) and slightly different punctuation.

Book (AD):

Smith, Jane. 2023. The Reading Mind. New York: Routledge.

Journal article (AD):

Smith, Jane, and Adam Jones. 2023. "Reading Speed and Aging in Monolingual 
Adults: A Longitudinal Study." Journal of Cognitive Aging 45 (3): 234-251. 
doi:10.NNNN/example.

The format mostly mirrors NB but with the date moved up. The reference list is alphabetical by surname.

Paper Formatting (Manuscript Layout, Turabian Conventions)

Chicago / Turabian formatting rules for thesis writing.

Margins

1 inch on all sides. Some universities require 1.5" on the left for binding.

Font

Times New Roman or Garamond 12pt is conventional. Some universities specify; check your handbook.

Spacing

Double-spaced throughout for the body text. Single-spaced for: block quotes, footnotes, bibliography entries (with blank lines between).

Indentation

First line of every paragraph: indented 0.5". Block quotes (5+ lines of prose): no quotation marks, single-spaced, indented 0.5" from the left margin.

Page numbers

For Turabian, page numbers go at the top right or bottom center, depending on chapter conventions. Title page (page 1) has no visible number. Front matter (table of contents, abstract) uses lowercase Roman numerals (i, ii, iii). Body uses Arabic numerals starting from 1 on the first body page.

Title page (Turabian)

Centered, distributed vertically:

1. Title (typically 1/3 down the page, bold)
2. Subtitle (if any, on a new line)
3. Author name (lower middle)
4. Submission statement (e.g., "A Dissertation Submitted to...")
5. Institution and department
6. City and date

This is for academic theses. Term papers use a simpler title page or a Chicago-style heading.

Chapter headings

Chapter title centered, in bold or in caps, 1/3 down the page. Section headings flush left, bold. Subsection headings flush left, italic. Use consistent levels throughout.

Key Changes: Chicago 18 vs Chicago 17

The official Chicago summary identifies substantial revisions throughout the manual. For citation work, the most visible changes include:

1. Author thresholds changed: bibliography and reference-list entries show up to six authors; for more than six, show the first three followed by et al.. Notes and author-date citations use shorter thresholds.
2. Repeated author names: Chicago now prefers repeating the author name instead of replacing it with a 3-em dash in successive bibliography entries.
3. Digital and AI sources: new or expanded guidance covers archived web pages, datasets, social media, podcasts and AI-generated content.
4. Accessibility: expanded recommendations cover electronic publications, images and mathematical content.
5. Inclusive language: generic singular they is explicitly endorsed as an option, with broader guidance on disability, identity and bias.
6. Capitalization and punctuation: the edition changes several title-case and punctuation rules, including capitalizing prepositions of five letters or more in title case.

Use the official What's New in the 18th Edition list when updating an existing Chicago 17 document.

Common Mistakes That Cost Points or Cause Re-Formatting

Five mistakes supervisors flag most often in Chicago papers.

Repeating full notes unnecessarily: use the shortened form defined by Chicago after the first full citation. Check any institutional rule on ibid..

Mixing NB and AD systems: pick one (NB for humanities, AD for sciences) and use it throughout. Mixing footnote-based and parenthetical citations in the same paper is forbidden.

Wrong format for first vs subsequent notes: the first footnote for a source is full; subsequent notes are shortened. Many writers default to short notes throughout (missing the full citation) or full notes throughout (cluttering the apparatus).

Bibliography vs Reference List confusion: NB uses "Bibliography"; AD uses "Reference List". Don't mix the labels.

Forgetting hanging indent: 0.5" hanging indent on bibliography/reference list entries is mandatory. Use your word processor's paragraph dialog, not manual tabs.

Reference Managers and Chicago 18

Reference managers can apply Chicago styles, but the installed style name and version must be checked:

• Zotero: select the exact Chicago 18 NB or AD style required by your program
• EndNote: verify the output style version before formatting the final document
• Mendeley: inspect generated notes and bibliography entries against the official examples
• Folio Student: associates thesis templates with Chicago 18 and prepares the bibliography section

Older installations may still expose Chicago 17 styles. Confirm both the edition and whether you need Notes-Bibliography or Author-Date, then manually review the generated output.

Submission Checklist (Chicago 18 Thesis or Paper)

• Decided NB or AD system (consistent throughout)
• Title page conforms to Turabian or university template
• Margins, typeface and spacing match the current institutional template
• Page numbers per Turabian convention (Roman for front matter, Arabic for body)
• First footnote for each source = full citation; subsequent = shortened form
• Shortened notes and any use of ibid. follow the required edition and local guide
• All in-text citations / footnotes match bibliography / reference list
• Bibliography or Reference List on a new page, label centered
• Hanging indent 0.5" on every entry
• Alphabetical order by first author's surname
• DOIs included when available (preferred over URLs)
• Italics for stand-alone works, quotation marks for articles and chapters
• Chicago 18 author thresholds applied to bibliography entries, notes and author-date citations
• Singular "they" used appropriately
• Capitalization conventions for racial identity terms applied
• Final proofread by a fresh reader

For full details on every academic standard, see our academic style guides reference. For comparison of APA, MLA, Chicago and Vancouver by discipline, see our doctoral thesis formatting guide. For the dominant social science standard, see our APA 7 complete guide. For literature and humanities, see our MLA 9 complete guide.

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FAQ

What is the current Chicago edition in 2026?

The current edition is CMOS 18, published in 2024. The official online service still provides access to CMOS 17 for users maintaining older projects, but new work should use the edition required by the institution or publisher.

Should I use Notes-Bibliography or Author-Date?
Discipline determines this. History, art, music, theology, classics, religious studies, and many humanities use Notes-Bibliography (NB). Some social sciences, business, and Chicago-format sciences use Author-Date (AD). Ask your supervisor at the start of your thesis: switching mid-writing is extremely painful.

What's the difference between Chicago and Turabian?
Chicago is the broader editorial reference. Turabian adapts Chicago-style research and citation guidance for student writers and includes academic-paper conventions. Turabian 9 remains the published edition as of August 2026; a 10th edition is announced for November 2026.

Why does Chicago have two systems?
Historically, Chicago accommodated both humanities (which prefer footnote-based citations with substantive notes) and sciences (which prefer in-text parenthetical citations for compactness). Modern CMOS continues this duality so that both communities can use Chicago without changing their citation culture.

Should I use ibid. in Chicago 18?

Chicago's regular short form is the safer default for repeated citations. If your university or publisher gives a specific instruction on ibid., follow that local rule consistently.

How do I cite AI tools in Chicago 18?

CMOS 18 adds guidance for AI-generated content, but the correct treatment depends on whether the output is publicly retrievable and on the role it played in the work. Follow the official Chicago guidance and your institution's disclosure policy; preserve prompts and outputs when they are part of the research record.

How do I cite an archival source?
Chicago has very detailed conventions for archives. The basic pattern:

Smith, Jane. Letter to John Doe. May 15, 1923. Smith Family Papers, Box 3, Folder 12, Special Collections, University of Chicago Library.

Include: creator, type of document, recipient (if a letter), date, collection name, box/folder, repository. This is one of Chicago's strengths over MLA or APA for archival research.

Are footnotes preferred over endnotes in Chicago?
CMOS allows both. Footnotes (at the bottom of each page) are more reader-friendly for citation-heavy work and are the norm in academic books. Endnotes (at the end of the chapter or paper) are sometimes preferred for journals and to keep page layouts clean. Your supervisor or program will indicate which to use.

What if my source has a DOI and a URL?
Use the DOI. CMOS 17 prefers DOIs over URLs because DOIs are stable. Cite as a permalink: doi:10.NNNN/example

Can I include both a Bibliography and a Reference List in the same thesis?
No. NB uses "Bibliography"; AD uses "Reference List". Use only the label that matches your chosen system.

How do I cite the Bible or other religious texts in Chicago?
For modern Bibles, identify the version in the first citation and abbreviate in subsequent notes:

1. The Holy Bible, New Revised Standard Version (Nashville: Thomas Nelson, 1989), Matthew 5:3.
2. NRSV, Luke 12:32.

The Bible and similar canonical texts are not always included in the bibliography (per CMOS); check your supervisor's preference.

Do I need to include access dates for online sources?
Only for time-sensitive content (Wikipedia, dashboards, social media). For stable scholarly URLs and DOIs, no access date is needed.