You can cancel at any time throughout the application process. The information retained in eVision depends on how far through the process you got before cancelling.
If you created a portal login but didn't submit an application to a programme prior to cancelling, all of your details are removed from eVision. If you apply again, you will need to complete all of the information (name, date of birth, email address) again.
If you submitted an application and then cancelled before receiving an offer, your personal details and details of the programme/s are retained. You'll be able to log in using your email address and password if you decide to apply again, and won't need to create a new account.
As yet, the University has not set a time period after which cancelled or incomplete applications will be permanently deleted.