I purchased a Voucher (AZ-900 Azure Fundamentals) back in January 2021? from a 3rd party Voucher Providers, which at the time was a good deal ($38.00US) and the voucher was good until Feb 28, 2021, which is good and fine at the time and was hoping to study and pass this exam by Feb 24 2021, but with work and limited time to study, I thought that by contacting (Microsoft-Pearson VUE) I could change the exam date to March 31, 2021, but what the Microsoft Agent told me on the phone, they couldn't change the exam date (anything past Feb 28 2021) because of that 3 Party Voucher). So what I learned from this experience is that be sure (100% sure) that you are prepared to write that exam by the date your planning to write it. The other option, I thought at the time is to BUY the Full Price Voucher on Microsoft website and that way if you think the timeline is too short or not enough time to the write that exam, that way you change or reschedule the exam date at a later date, in my case march 31 2021. I hope this is helpful and clear in my message. Dan