I have SCJP exam in other four days. I have registered for 25th of May. As I didnot prepare much , I would like to postpone it now. I have registered for the exam with a voucher which expires on May 26th. Is it possible to postpone this exam now?
Actual registration and appearing for the exam takes place right after you arrive at the centre and you can postpone the exam as long as your voucher doesn't expire.
So, call your exam centre people and inform them.