Competing interests for reviewers: A guide to ethical peer review

Reviewer Resources > How to proceed when you are invited to review > Competing interests for reviewers: A guide to ethical peer review

As a reviewer, you help uphold the integrity and quality of the scientific record. That is a significant responsibility—but you are not expected to navigate it alone.

This guide is here to support you in identifying and declaring competing interests—an essential part of ensuring that peer review remains fair, transparent, and trustworthy.

What are competing interests—and why do they matter?

Competing interests are any relationships or circumstances that could interfere with—or be perceived as interfering with—your ability to provide an objective and unbiased review. They include anything that could influence, or be reasonably perceived to influence, the peer review process, editorial decision-making, or publication of the work.

These can be:

Financial (e.g., potential for personal gain or loss)
Personal (e.g., close relationships or rivalries)
Professional (e.g., recent collaborations or shared affiliations)

We consider a competing interest to be:

Anything that interferes with, or could reasonably be perceived as interfering with, the full and objective presentation, peer review, editorial decision-making, or publication of research or non-research articles submitted to us.

Even the appearance of bias can undermine the credibility and trust in the review process. That is why transparency is essential—even if you believe your review remains impartial.

How to check for competing interests

You should assess potential conflicts before accepting a review invitation and again after accessing the full manuscript. Reviewing at both stages helps ensure that no relevant conflicts are missed. Ask yourself:

Financial conflicts

Could I benefit financially from the publication or rejection of this research?

Personal conflicts

Do I have a personal relationship with any of the authors?
Am I in direct competition with the authors?

Professional conflicts

Have I worked at the same institution as the authors within the last 5 years?
Have I collaborated or published with the authors in the past five years?
Do I share current or recent grant funding with any of the authors?

Where to look in the manuscript

Author list: Do you recognize any names?
Funding section: Are there shared grants?
Acknowledgements: Are you mentioned or thanked?

What to do if you identify a competing interest

If you identify a potential conflict—whether listed above or not—contact the journal immediately. Do this before proceeding with your review. The editorial team will assess the situation and may:

Reassign the manuscript to another reviewer, or
Ask you to proceed with the review while transparently declaring the competing interest in your comments.

Remember: having a competing interest is not inherently unethical. Failing to disclose it is. Transparency allows editors to make informed decisions and maintain trust in the peer review process.

Ethical principles for reviewers

These recommendations are based on the COPE Ethical Guidelines for peer reviewers, which PLOS follows as a member of the Committee on Publication Ethics:

Choose assignments wisely: Only accept reviews you are qualified for and can complete on time. In some instances, we welcome reviewers if your expertise is limited to some aspects of the study. Please let the editorial team know if that is the case.
Be objective and fair: Avoid bias based on personal beliefs, affiliations, or demographics.
Maintain confidentiality: Do not share or use manuscript content outside the review process including in AI tools.Any use of AI tools in peer review (e.g. for data assessment, translation, or language editing) must be clearly disclosed to authors in the review form (reviewers) or decision letter (editors). Further information is available here.
Be respectful and professional: Focus your feedback on the research, not the researchers.