Hello, I have a question: if I book an exam A using a voucher, but then I have to cancel the exam and would like to book an exam B using that voucher, can I do it? Or can I no longer use the voucher even if I canceled exam A? Thanks.

Hi, For general policies and processes, visit the Salesforce Exam Reschedule and Cancellation Policy. If you cancel an exam for which you used an exam voucher as payment, the exam voucher will be restored. If your exam voucher has not expired, you can reuse the exam voucher code to reschedule an exam. 

https://help.salesforce.com/s/articleView?id=005298925&type=1