How to change the corresponding author – JMIR Publications

Note on terminology:

The submitting user is the user who can login into the manuscript homepage and see and respond to all communications.
The corresponding author appears in the manuscript as "Corresponding Author" and is indicated in the metadata form as such (there is a radio button to select one of the authors as corresponding author in the metadata form).
The corresponding author may or may not be identical with the submitting user. In other words, it is entirely possible to publish a manuscript where the published corresponding author is not the submitting author (the submitting user doesn't even have to be an author), and vice versa.

To change the roles between authors:

To change the corresponding author (what shows up in the published article), edit the metadata form (there is a radio button to select one of the authors as corresponding author in the metadata form) - see also Change your author details before publication.
To change the submitting user (who can see and edit the submission), read How to change the submitting author, i.e. hand over the manuscript to a co-author for further editing and communication with the editorial office?