10 Common Citation Mistakes and How to Fix Them
Avoid the most frequent citation errors students make, from missing DOIs to incorrect et al. usage.
Citation errors are one of the most common reasons students lose marks on papers. Most are easy to fix once you know what to look for. Here are the ten mistakes we see most often, with the fix for each.
1. Missing DOI When One Exists
The mistake: Omitting the DOI from a journal article citation, even though the article has one.
Why it matters: DOIs are permanent links. URLs can break, but DOIs always resolve to the current location. Most styles now require them when available.
The fix: Search for the DOI on CrossRef before finalizing any journal article citation. If a DOI exists, include it. Learn more in our DOI guide.
2. Using "et al." Incorrectly
The mistake: Using "et al." for two-author works, or using it in the reference list instead of just in-text.
The rules:
- APA: Use "et al." for 3+ authors in-text. List all authors in the reference list (up to 20).
- MLA: Use "et al." for 3+ authors in-text. List the first author + "et al." in Works Cited.
- Chicago: Use "et al." for 4+ authors in footnotes. List all in bibliography (up to 10).
The fix: Never use "et al." for two-author works in any style.
3. Wrong Title Capitalization
The mistake: Using title case everywhere, or sentence case everywhere, regardless of the style.
The rules:
- APA article titles: Sentence case (The impact of citation accuracy)
- APA journal names: Title case (Journal of Academic Writing)
- MLA: Title case for everything
- Chicago: Title case for everything
The fix: Check what your style requires for each element (article title vs. journal title vs. book title). They often differ.
4. Inconsistent Citation Style
The mistake: Mixing APA, MLA, and Harvard formatting in the same reference list -- or using APA in-text citations (Smith, 2025) but MLA-formatted Works Cited entries. This often happens when copying citations from different sources or switching tools mid-project.
The fix: Choose one style from the start and format all citations in one batch. Don't copy-paste from Google Scholar or databases without reformatting. If you need to switch styles, convert everything at once -- CiteTools batch mode converts your entire reference list in one step.
5. Missing Hanging Indent
The mistake: The reference list uses standard paragraph formatting instead of hanging indent (first line flush left, subsequent lines indented 0.5 inches).
Why it matters: APA, MLA, Chicago, and Harvard all require hanging indent. It's one of the first things professors check.
The fix: Select all reference entries in Word, go to Paragraph > Indentation > Special > Hanging (0.5").
6. Incorrect Date Formatting
The mistake: Using different date formats across entries, or using the wrong format for your style.
The formats:
- APA: (2025) in parentheses after author
- MLA: 15 Mar. 2025 (day-month-year, abbreviated)
- Chicago: March 15, 2025 (month-day-year, spelled out)
- Vancouver: 2025 (year only for journals, full date for websites)
The fix: Pick the format your style requires and apply it consistently.
7. Not Citing Paraphrased Content
The mistake: Thinking citations are only needed for direct quotes.
The reality: Every idea that came from a source needs a citation, whether you're quoting directly, paraphrasing, or summarizing. The only exception is common knowledge (facts that would appear in a general encyclopedia).
The fix: If you can point to a specific source where you learned the information, cite it. See our paraphrasing guide for details.
8. Wrong URL Format
The mistake: Using shortened URLs, archive URLs, or database-specific URLs that won't work for other readers.
The fix:
- Use the DOI URL when available (always works)
- Use the publisher's URL, not your library's proxy URL
- Don't use URL shorteners
- Check that the URL actually loads the source
9. Missing Access Date for Online Sources
The mistake: Omitting the date you accessed a web source in styles that require it.
When it's required:
- Harvard: Always required for online sources
- Vancouver: Always required cited YYYY Mon DD
- Chicago: Required when no publication date is available
- APA: Not required (APA 7th dropped this requirement)
- MLA: Not required unless instructor asks
The fix: Record the access date when you first visit the source. It's tedious to track down later.
10. Not Citing Paraphrased Content
The mistake: Putting someone else's idea in your own words and assuming you no longer need a citation. Paraphrasing without citing is still plagiarism.
Why it happens: Students think citations are only for direct quotes. In reality, any idea, finding, or argument that originated elsewhere needs attribution -- even if you've completely reworded it.
The fix: If the idea isn't yours, cite it. Only common knowledge (facts no one would dispute) can go without a citation. When in doubt, cite. See our guide on how to paraphrase without plagiarizing for detailed examples.
Try It with CiteTools
Most of these mistakes come from manual formatting. Paste any citation, DOI, or URL into CiteTools.io and get a correctly formatted reference -- no memorization required.
For a step-by-step approach, see how to build a reference list from scratch. Starting a new semester? Check our back-to-school citation habits guide.