The deadline for submitting a revised manuscript is provided in the editorial decision email (see also I am an author - where can I find the past reviewer comments?).
After an editorial decision B (minor revisions) or C/D (revisions/ major revisions required) has been made, authors usually have 1 week (B), 3 weeks (C) or 4 weeks (D) to submit responses to reviewers and the revised version (see also How do I respond to reviewer comments and upload a revised manuscript?). If we do not receive a revision by this deadline, the manuscript may be removed from the submission queue. However, if the authors do not intend to submit a revision, we require a formal withdrawal.(see How do I withdraw a submitted (but not published) article from peer-review?).
Authors can request an extension of the revision deadline, by a maximum of 6 weeks (after the original deadline), using the revision upload form. Please note that after the first extension, additional extensions will be reviewed by the Editor. The Editor may decline the extension if the data is time sensitive.
The extension request is made on the form where you would submit your revision (click on the link "awaiting revision" on the author homepage), as shown in the screenshot below.
See also: