For third time enrolment? If so, it's called "third time enrolment", which might be why you can't find anything. That abbreviates to "3TE". For EFS, as you may be aware, it's done all in-house. Call (don't email, call) the department and they'll put you onto the person... forgot her name, but this time last semester it was a british/irish/similar lady. ...And, as per all approval/waiver things, any time prior to you enrolling (or attempting to enrol) in the unit is fine.
If all else fails, email eStudent support and they'll tell you more (Though if you're unlucky I might be on the other end of the email and copy and paste the above back to you ).
i actually called before i saw your reply, spoke to an absolute random in efs dept who adv its due after this semesters results are out, he said there was no submit by date but that i had to do it straight away ??
anyway i emailed another random to just get it in writing and she sent back a similar respone in slightly broken english, im not too trusting with their responses so will try to get in touch with this british/irish lady lol