What Is Self-Plagiarism? Why Reusing Your Own Work Can Still Be a Problem

The reused material can be a whole paper, a passage, or a dataset. It becomes self-plagiarism when you present it again without telling the new reader that you already submitted or published it. The University of Missouri's Office of Academic Integrity notes that self-plagiarism is sometimes called text recycling. Its student example is a paper from an earlier course, turned in for a new one with small changes to the headings. The U.S. Office of Research Integrity (ORI) calls the same pattern double-dipping. A whole paper, or a substantial part of one, that already met one course's requirement is used again to meet a requirement in a different course, taught by a different instructor. Our overview of what plagiarism is covers the other forms.

Reusing your own work is not the same wrong as taking someone else's, which is what plagiarism usually means. No one is denied credit. The U.S. Office of Research Integrity (ORI) raises that objection itself: because plagiarism is often thought of as theft, self-plagiarism "does not seem to make much sense." It still treats the practice as a problem, because it "misleads the reader about the novelty of the material." The same page notes that the U.S. research-misconduct regulation, 42 CFR Part 93, does not consider self-plagiarism to be research misconduct. ORI's definition of research misconduct lists fabrication, falsification, and plagiarism in proposing, performing, or reviewing research, or in reporting research results. Reusing your own published material is not on that list.

Institutions and journals fill the gap the federal rule leaves. The school and journal policies described below all restrict undisclosed reuse. Their concern isn't ownership. It's whether a reader, instructor, or editor is misled into thinking they're looking at new work, new data, or a full attempt at an assignment.

Not every case carries the same weight. A research taxonomy summarized by the American Society for Microbiology sorts reuse by how finished the original material was. In that taxonomy, reusing unpublished material such as talks or posters is generally acceptable, unless the original is widely available. Reusing methods language from a published paper depends on disclosure and on how much text is recycled. Republishing earlier work with little change for a similar audience is rarely acceptable.

For journal publishing, the International Committee of Medical Journal Editors (ICMJE) draws the line at disclosure rather than at reuse itself. In its definition, duplicate publication means publishing a paper that overlaps substantially with one already published, without clear, visible reference to the earlier version. If a manuscript reports work that is already published in large part, or is closely related to a paper submitted or accepted elsewhere, the submission letter should clearly say so.

Policies vary by school and by journal, so there is no one rule to quote. The University of Toronto's academic-integrity guidance treats resubmitting an already-graded assignment as an offense and tells students to always ask the instructor for permission first. Missouri's page frames the same advice around deception. In its words, "If the instructor knows what you are doing, then you are not deceiving the reader."

Originality-checking software gives you a practical reason to disclose early. At Utrecht University, papers stored in the checker's database are compared with later submissions, as its plagiarism-check guidance explains. A resubmitted paper, or a lightly revised version of it, can then show up as a match against your own earlier submission. Whether a paper is stored depends on a setting chosen when the assignment is created, and the instructor judges what a match means. Our guide to reading a similarity report shows how such a match appears.

• Read the policy that applies first. Check the syllabus, the student handbook, or the journal's author guidelines for whether reuse needs permission, and from whom.
• Ask and disclose before you submit, not after. Tell the instructor or editor about the earlier version up front. The policies above judge reuse largely by whether that person knew about it beforehand.
• Cite yourself. Quote or paraphrase your earlier paper with a citation, in the formats shown in the next section. The rules for citing a paraphrase apply to your own work too.
• Check the overlap before you submit. If you're not sure how much of a new piece repeats an earlier one, the Certentis plagiarism checker shows which passages match sources it can find, so you can decide what to disclose and cite. It finds your earlier piece only if that piece is among those sources, as a published article may be. An unpublished class paper may not be, so compare the two files side by side.

Once the reuse is cleared, cite the earlier work the way you would cite any other source, as the MLA Style Center advises. Published work gets the normal reference for its type. A paper you handed in for another course counts as an unpublished manuscript, as the James Cook University (JCU) library notes.

The APA course-paper row follows APA Style's model for unpublished manuscripts. JCU's guide labels the same case [Unpublished assignment submitted for EL1006], with the subject code. Use the label your instructor expects. JCU also advises referring to a past assignment only when you have been explicitly asked to, for example in a reflective task.

Citing yourself in the text

In the text, cite yourself like any other author: (Lee, 2024) in APA, (Lee 4) in MLA. A narrative form also works: "In earlier work (Lee, 2024), I argued that …" APA Style tells a single author to write "I," and MLA allows it too. JCU's guide calls third person the general convention, so check what your course expects.

Worked example: reusing two sentences from a course paper

The student and paper are fictional. Jordan Lee wants to reuse two sentences from a 2024 sociology paper in a new course, and the new instructor has agreed.

• Original, page 4: "Commuter students in the sample studied mainly in the library. Several left campus right after their last class."
• New sentence: In an earlier course paper, I found that "commuter students in the sample studied mainly in the library" and that several "left campus right after their last class" (Lee, 2024, p. 4).
• APA reference entry: Lee, J. (2024). Where commuter students study [Unpublished manuscript]. Department of Sociology, Example University.

Restating the finding in new words still needs the citation, as our guide on how to cite a paraphrase explains.