If you are registered for a course, you are automatically registered for the exam. You can check this in GLASS. For some courses, you can take an examination without taking the course. You then have to register for the option TGOW (Tentamen Geen Onderwijs, Examination without course participation) of this course in GLASS. But for most courses, this option does not exist. You can see whether this option is available in GLASS.
If you have registered for the course, you are also registered for the resit. It doesn't matter whether you took part in the first opportunity. This is slightly different for first-year subjects. Here, attendance is compulsory in order to take the resit. In the Course Catalogue you can see how it works for each course.
You cannot cancel an exam registration, only deregister for the course. If you do not want to take the exam, but you want to take the resit, then leave your registration for the course. If you are ill during the exam, you can take part in the resit.
You can participate in the resit if you are registered for a course. It does not matter whether you took part in the first exam opportunity and what the result was. But the last mark you obtained counts. Even if it is lower than the previous grade.
Did you register for a course but did not take part in the exams? If so, you will receive the message non attendance (NAP) in SIS and on an uncleared list of marks. This stands for not present with attempt. A NAP has no effect on the cum laude regulation and will not be mentioned on your degree certificate.
Want to know more? Check the page on examinations en resits.