Step by step guide to reviewing a manuscript

When invited to peer review, you'll receive the manuscript's abstract to help you decide whether to accept the invitation and conduct the review. Respond promptly to avoid delays and declare any potential conflicts of interest early. Editors rely on timely, constructive feedback for decision-making. Provide clear, helpful comments—vague or unhelpful ones offer little value. Your review should include comments to the authors and possibly confidential ones to the editors. Remember, while peer review is often anonymous, never include anything in your report that you wouldn't discuss with the author in person.

The first read-through of a manuscript

You should already understand the aims, key data, and conclusions of the manuscript from reading the abstract provided in the invitation. If any of these aspects are unclear, make a note to address how they could be improved in your review.

Your first read-through should be a quick skim to form an initial impression of the paper and give you an idea of whether your final recommendation will be to accept, revise, or reject the paper.

Key considerations during your first read-through

• Take notes: Keep a pen and paper nearby for jotting down your thoughts, including line numbers. This makes it easier to reference specific sections when writing your review.
• Research relevance and originality: Ask yourself if the main question addressed by the research is interesting, relevant, and original. How does the manuscript contribute to the field compared to existing studies?
• Clarity and quality: Is the paper clearly written, and is the argument easy to follow? Evaluate whether the authors’ conclusions are well-supported by the evidence presented. If the author disagrees significantly with the current academic consensus, do they have a substantial case? If not, what would be required to make their case credible?
• Data presentation: Assess whether the tables, figures, and images effectively support the manuscript's findings or if they seem unnecessary.

Identifying major flaws

Focus on finding major issues that could affect the manuscript’s credibility or reliability. Key flaws may include:

• Conclusions contradicting the evidence: Are the conclusions supported by the data, or do they contradict the author's own statistical or qualitative data?
• Methodological concerns: Are outdated or unreliable research methods used? Check that the methodology aligns with best practices for replicability and robustness.
• Overlooking key processes: Has the author ignored a process that is known to have a strong influence on the area under study?

When reviewing a paper with a focus on experimental design, ensure the methodology is robust. Key areas to assess include:

• Sampling methods in analytical papers
• Sufficient use of control experiments
• Precision of process data
• Regularity of sampling in time-dependent studies
• Validity of research questions, the use of a detailed methodology, and the data analysis being done systematically (in qualitative research)
• That qualitative research extends beyond the author's opinions, with sufficient descriptive elements and appropriate quotes from interviews or focus groups

Major flaws in information

If methodology appears sound, next examine the data tables, figures, or images, especially in scientific research where data quality is crucial. If there are critical flaws in this, it's very likely the manuscript will need to be rejected. Look for:

• Insufficient data
• Unclear data tables
• Contradictory data that either are not self-consistent or disagree with the conclusions
• Confirmatory data that adds little, if anything, to current understanding - unless strong arguments for such repetition are made

Document any issues with clear reasoning and supporting evidence, including citations, to strengthen your review.

Concluding your first read

After reviewing the paper, draft the first two paragraphs of your review:

• Paragraph 1: Summarize the research question, methodology, goals, and conclusions to help the editor contextualize the research and add weight to your judgement. Highlight the key messages conveyed to the reader, so the author is confident they are achieving their intended goals. Emphasize the paper's successful aspects to help the author recognize their strengths.
• Paragraph 2: Provide a conceptual overview of the manuscript’s contribution to the field. Does the paper introduce new, significant findings? Are the methods appropriate and the data reliable?

These paragraphs will help you decide if the manuscript is seriously flawed and should be rejected, or if it's publishable in principle and warrants further review.

Even if you spot serious flaws, read the entire paper to identify any positive aspects to share with the author. A full read-through will also make sure that any initial concerns are indeed correct and fair. After all, you need the context of the whole paper before deciding to reject.

Next steps: The second read-through

After the first read-through and deciding the paper is publishable in principle, the second detailed review aims to refine the manuscript for publication. You may still decide to recommend rejection following a second reading.

Tips to save time and simplify the review:

• Make separate notes instead of relying solely on manuscript comments.
• Group similar concerns or praise for easier reference. If using a review program to note directly onto the manuscript, still try grouping the concerns and praise in separate notes—it helps later.
• Keep images, graphs, and data tables visible—either printed or on a second monitor.

During this stage focus on:

• Argument construction: Identify unclear or ambiguous sections, factual errors, or invalid arguments.
• Clarity and style: Evaluate whether the title accurately reflects the paper's subject, and whether the abstract provides a clear, accessible summary of the research. Check that the keywords align with the content and that the paper is an appropriate length, with key messages being concise, accurate, and easy to understand.
• Language: Your role is to judge the research content and ensure the paper's meaning is clear, not to fix language issues. If the writing is poor but understandable, suggest improvements, such as clarifying parts of the discussion or advising the authors to resubmit after language revisions. Grammar and punctuation should only be addressed if they affect clarity, as editors will handle final language polishing. Expect to suggest such amendments —it's rare for a manuscript to pass review with no corrections.

Section by section guidance

1. The Introduction

The introduction should clearly set out the research argument and summarize recent literature related to the topic. It should highlight existing gaps in knowledge or conflicts in current understanding, establishing the need for the research. Ensure the introduction gives a clear idea of the target audience, demonstrates the originality of the research, explains its novelty, and justifies why the study is timely and important.

Originality and topicality

Originality and topicality can only be established in the light of recent authoritative research. For example, it's impossible to argue that there is a conflict in current understanding by referencing articles that are 10 years old.

Authors may make the case that a topic hasn't been investigated in several years and that new research is required. This point is only valid if researchers can point to recent developments in data gathering techniques or to research in indirectly related fields that suggest the topic needs revisiting. Clearly, authors can only do this by referencing recent literature. However, it is perfectly appropriate for authors to cite some older papers where research is seminal, or aspects of the methodology rely upon it.

Research aims

The introduction typically ends by stating the research aims. These should be clear from the introduction, and if the aims are a surprise, the introduction needs improvement.

2. Materials and Methods

Academic research should be replicable, repeatable and robust - and follow best practice.

Replicable research: The study should make sufficient use of control experiments, repeated analyses and experiments, and adequate sampling to confirm that observed trends are not due to chance. Statistical analyses will not be sound if methods are not replicable. Where research is not replicable, the paper should be recommended for rejection.

Repeatable methods: These should give enough detail so that other researchers can do the same research. The equipment used, or sampling methods, should all be described so that others could follow the same steps. Where methods are not detailed enough, it's usual to ask for the methods section to be revised.

Robust research: A sufficient number of data points is necessary to ensure the reliability of the findings. It is appropriate to recommend revisions if there is insufficient data. Additionally, any potential biases in the methodology that are not addressed through control experiments should be considered.

Best practice: The study must follow established standards, such as the CONSORT Statement for randomized trials, and with no compromise to the health and safety of all participants. Ethical standards should be strictly adhered to. If the research fails to reach relevant best practice standards, it's usual to recommend rejection. In such cases, you don't need to read any further.

3. Results and discussion

This section should provide a clear and coherent narrative, answering key questions: What were the findings? What new insights were gained?

Certain patterns of good reporting need to be followed by the author:

• They should start by describing in simple terms what the data show.
• They should refer to statistical analyses, such as significance or goodness of fit.
• Once described, they should evaluate the trends observed and explain the significance of the results to wider understanding. This can only be done by referencing published research.
• The outcome should be a critical analysis of the data collected.

Discussion should always, at some point, gather all the information into one whole. Authors should describe and discuss the overall story formed. If there are gaps or inconsistencies in the story, they should address these and suggest ways future research might confirm the findings or take the research forward.

4. Conclusions

This section is usually no more than a few paragraphs and may be presented as part of the results and discussion, or in a separate section. The conclusions should reflect upon the aims —whether they were achieved or not —and, just like the aims, should not be surprising. If the conclusions are not evidence-based, it's appropriate to ask for them to be re-written.

5. Information gathered: images, graphs and data tables

If you find yourself looking at a piece of information from which you cannot discern a story, then you should ask for improvements in presentation. This could be an issue with titles, labels, statistical notation, or image quality.

Where information is clear, you should check that:

• The results seem plausible, in case there is an error in data gathering
• The trends you can see support the paper's discussion and conclusions
• There is sufficient data. For example, in studies carried out over time are there sufficient data points to support the trends described by the author?

You should also check whether images have been edited or manipulated to emphasize the story they tell. This may be appropriate but only if authors report on how the image has been edited (e.g., by highlighting certain parts of an image). Where you feel that an image has been edited or manipulated without explanation, you should highlight this in a confidential comment to the editor in your report.

6. List of references

You will need to check referencing for accuracy, adequacy, and balance.

Accuracy: Where a cited article is central to the author's argument, you should check the accuracy and format of the reference —and bear in mind different subject areas may use citations differently. Otherwise, it's the editor’s role to exhaustively check the reference section for accuracy and format.

Adequacy Assess the adequacy of the references by determining if they adequately support the manuscript's claims and if there are any significant studies, both similar and opposing, that should be cited but are missing. A reference list that is too sparse or relies heavily on a limited number of sources may indicate that additional references are needed, though avoid judging solely by quantity. Ensure the references are current, relevant, and easily retrievable.

Balance: Check for a well-balanced list of references that is helpful to the reader, fair to competing authors, and not over-reliant on self-citation. The reference should recognize the initial discoveries and related work that that led to the work under assessment. You should be able to evaluate the balance of the references without looking up every single citation but should raise any concerns if certain perspectives seem underrepresented.

7. Plagiarism

If you suspect plagiarism, thoroughly assess the paper’s originality.

Identified concern: If you find —or already knew of —a very similar paper, this may be because the author overlooked it in their own literature search, or because it is very recent or published in a journal slightly outside their usual field. You may advise the author how to emphasize the novel aspects of their own study, to better differentiate it from similar research. If so, you may ask the author to discuss their aims and results, or modify their conclusions, considering a similar article. Of course, if the research similarities are so great that they render the work unoriginal, you may have no choice but to recommend rejection.

Suspected concern: If you suspect plagiarism, including self-plagiarism, but cannot recall or locate exactly what is being plagiarized, thoroughly assess the paper’s originality. Most editors have access to software that can check for plagiarism. Editors are not out to police every paper, but when plagiarism is discovered during peer review it can be properly addressed ahead of publication. If plagiarism is discovered only after publication, the consequences are worse for both authors and readers, because a retraction may be necessary. For detailed guidelines see our Best Practice Guidelines on Research Integrity and Publishing Ethics.

How to structure your report

Summary

• Give positive feedback first. Authors are more likely to read your review if you do so. But don't overdo it if you will be recommending rejection.
• Briefly summarize the paper’s content and findings.
• Put the findings in the context of existing literature, noting the work's significance and originality.
• Indicate the significance of the work and if it is novel or mainly confirmatory. Highlight the work's strengths, quality, and completeness.
• State any major flaws or weaknesses and note any special considerations. For example, if previously held theories are being overlooked.

Major issues

• Are there any major flaws? State what they are and what the severity of their impact is on the paper
• Has similar work already been published without the authors acknowledging this?
• Are the authors presenting findings that challenge current thinking? Is the evidence they present strong enough to prove their case? Have they cited all the relevant work that would contradict their thinking and addressed it appropriately?
• If major revisions are required, try to indicate clearly what they are
• Are there any major presentational problems? Are figures and tables, language and manuscript structure all clear enough for you to accurately assess the work?
• Are there any ethical issues? If you are unsure it may be better to disclose these in the confidential comments section.

Minor issues

• Are there places where meaning is ambiguous? How can this be corrected?
• Are the correct references cited? If not, which should be cited instead/also? Are citations excessive, limited, or biased?
• Are there any factual, numerical or unit errors? If so, what are they?
• Are all tables and figures appropriate, sufficient, and correctly labelled? If not, say which are not.

Peer review presentation and style

Your review should ultimately help the author improve their article. Be polite, honest, and clear. Try to be objective and constructive. You should also:

• Write clearly, avoiding complex language that may confuse non-native English speakers.
• Number your points and refer to page and line numbers in the manuscript when making specific comments
• If asked to review only certain aspects, state which ones clearly.
• Treat the author's work the way you would like your own to be treated.

Criticisms and confidential comments to editors

Most journals give reviewers the option to provide confidential comments to editors. Often this is where editors will want reviewers to state their recommendation, but otherwise this area is best reserved for communicating malpractice such as suspected plagiarism, fraud, unattributed work, unethical procedures, duplicate publication, bias, or other conflicts of interest.

Remember that authors can't see this feedback and are unable to give their side of the story unless the editor asks them to. However, you should still write comments to editors as though authors might read them too.

Peer review recommendations

Reviewers should check the preferences of individual journals as to where they want review decisions to be stated. Bear in mind that some journals will not want the recommendation included in any comments to authors, as this can cause editors difficulty later. You will normally be asked to indicate your recommendation (e.g., accept, reject, revise, and resubmit) from a fixed-choice list and then to enter your comments into a separate text box.

Recommending acceptance: Provide details outlining why, and if there are any areas that could be improved.

Recommending revision: Where improvements are needed, a recommendation for major or minor revision is typical. You may also choose to state whether you opt in or out of the post-revision review too. If recommending revision, state specific changes you feel need to be made. The author can then reply to each point in turn. Some journals offer the option to recommend rejection with the possibility of resubmission—this is most relevant where substantial, major revision is necessary.

Recommending rejection: Where manuscripts have serious flaws you should not spend any time polishing the review you've drafted or give detailed advice on presentation. In your recommendations for the author, you should:

• Give constructive feedback describing ways that they could improve the research.
• Keep the feedback focused on the research and not the author. This is an extremely important part of your job as a reviewer.
• Avoid making critical confidential comments to the editor while being polite and encouraging to the author—the latter may not understand why their manuscript has been rejected. Also, they won't get feedback on how to improve their research and it could trigger an appeal.

Remember to give constructive criticism even if recommending rejection. This helps developing researchers improve their work and explains to the editor why you felt the manuscript should not be published.