Once your institution invites you to complete your Sprintax Calculus application, they will give you a deadline to fill out your account.
The deadline your school may give you depends entirely on them, however most institutions provide the timeframe of several months prior to locking the account.
Once the deadline passes, your account will be locked by your institution and you will not be unable to edit any information.
Therefore, it's very recommended you start completing your Calculus account as soon as possible in order to avoid such situation.