In the programme PSTS students register for each course that they will participate in through Osiris. It is common practice at the UT to register for a course before it’s start. If you sign up for a course, you are automatically also signed up for the first attempt of the assessment(s) of that course, be it an examination sitting, a final paper or any combination of exam, assignments and final papers. If you need to participate in the retake; the second attempt of an exam sitting/ paper deadline, you need to register for this retake separately. This registering for retakes is open in Osiris between 40 to 14 days ahead of the examination sitting or deadline.
Registering means that you want your assessment material to be assessed and it requires timely handing in of all your work. Missing an assignment means a lower grade or no grade at all, depending on the assessment standard of the course. Note that not registering means that your work will not be graded. Not de-registering and no performance means that one attempt is registered as NV (=no performance) in OSIRIS.
Signing out is possible until one day ahead. The date of reference is the assessment date in OSIRIS. That is the date of the examination sitting or when there is none, the deadline for turning in all required work.
Reference to recent communication: https://www.utwente.nl/nieuws/!/2012/8/249973/wijzigingen-procedure-in-en-uitschrijven-schriftelijke-tentamens