One of the coauthors withdraws their authorship after submitting a paper

It’s definitely weird, and a clear indication that something is going on with a paper. Basically, I can see two cases were this could happen, and both are not exactly great signs for the quality of a submission:

• The removed author was just a “courtesy author” without any real impact on the work. (S)he wanted to tag along at first, but now when people started to nag her/him to do real work, (s)he is rather out. In this case, it is ethically entirely okay to proceed without the additional author, but one wonders why the courtesy author was on the paper in the first place. While this does not say something about the quality of the paper per se, it leaves a certain sour taste in the mouth with regards to the ethics of the rest of the authors.
• The removed author was a “real” author in the sense that (s)he actually contributed to the work, but now feels that the submission is either so bad that (s)he does not want to be associated with it, or that the results are in fact wrong or unethically generated (e.g., because the co-author assumes that all or part of the work of somebody else was fabricated or is otherwise inaccurate). I think I do not have to explain why this would be a very bad sign for the quality of a submission.

What I would suggest in terms of procedure is full disclosure. Don’t just silently remove the author — in this case, the thoughts of the editor are very likely to wander to the two cases above, and this will make him look very carefully at your submission. Explain exactly what happened, and make sure to explain how it has nothing to do with the quality of the submission. If you can’t do that (e.g., because the co-author actually withdrew because (s)he thinks your results are wrong), it is simply better for everybody to withdraw.

What to do depends first on the reasons for the author withdrawing:

• If the person performed critical work, and the others cannot stand behind the full paper without them (e.g., the person actually gathered the data on which the paper is based), then the paper must be withdrawn and modified accordingly.

• If, on the other hand, the rest of the authors can and do stand behind the remainder of the paper, then the paper can simply go forward with that author removed.

Different journals have different procedures for removing an author, depending on their submission and manuscript management system. With some, the authors can edit the data themselves, with others, you need to do it through the editors. In either case, an explanation of the withdrawal should be sent to the editors, so that they know why the change and can decide whether it affects their judgement of the paper.

Changes in number of authors is not uncommon. There are many reasons for it, not by far only because of problems.

If you submit a manuscript to a journal and you need to have the authorship list changed (not just re-arranged), the easiest way is to wait until the reviews have come back and you, hopefully, are in a situation to make revisions. You then change the authorship list and provide the editor with a clear explanation of why the list has been changed.

It is of course common sense to send an e-mail to the editor as soon as possible and provide the information on changes and reasons why. The editor can then act as she or he sees fit. It could involve providing the reviewers with the information or not take any action at all, but at least you have been up-front with the information.

Remember that when you submit a manuscript there is commonly agreements in place that concerns all authors so providing the journal with changes in authors can be important to the journal.