Every registered exam can be deregistered up to three working days before the actual exam date.
Sunday is omitted (this is not a working day), the examination day is counted, so if you want to cancel an examination taking place on Monday, you must cancel it no later than the Thursday before: Friday 1st working day, Saturday 2nd working day, Sunday does not count, Monday = examination day 3rd working day).

It is possible to deregister via Selma/HISQIS for written examinations; for all other examinations, deregistration with confirmation of the date via a form is required.
In the case of repeat examinations, deregistration is only possible if there is no conflict with the retake deadline.

This does not apply to teacher training courses, please ask at the ZLSB!