Q: Can I change the corresponding author at the time of revision?
I didn't notice that I am listed as both first author and corresponding author when I submitted the paper. I want to change it now and move my supervisor who is second author to corresponding author. But right now paper is still under revision and not accepted yet. It seems impolite to change it suddenly. When can I mail journal to explain this situation which won't be impolite nor offending to editor? Do you have any mail template regarding this matter to share?
The corresponding author is the person who is responsible for all correspondences regarding the paper, including correspondences with the journal. Thus, changing the corresponding author would mean that all communication with the journal will have to be done by your supervisor. You should first find out whether he/she has the time for that. Moreover, since you have communicated with the journal so far, it would be preferable not to change the corresponding author unless absolutely necessary as this may create confusion. However, if you feel that the change is necessary, you can write to the journal explaining that you wish to change the corresponding author and that all future correspondences should be directed to this person.
Another option would be to ask if the journal would allow two corresponding authors. In that case, you can continue communicating with the journal as before, and your supervisor can just be added on cc to all future emails. However, remember that not all journals allow this.