No, once you have selected an exam mode and successfully paid the registration fee, AIMA does not allow you to change the mode (e.g., from PBT to CBT). However, if you originally registered for only one mode, you can often add a second mode (PBT+CBT) by paying the differential fee before the registration deadline for that session. If you missed the deadline or want to change entirely, you would need to register afresh for the next quarterly session (May, September, or December).