Collecting Deposits from Returning Student

(edited subject line for clarification)

We are trying to figure out a good process for charging our returning students an enrollment deposit (for the Spring 20xx → Fall 20xx cycle). We see where we can set the New vs. Returning student Enrollment Deposit fees in Billing Management → Billing → Billing Years → Enrollment Deposits. But what is the process for assigning this to the current students? And can we set up a block on registering for the Fall semester if they do not pay by a certain date? Or does this all need to be done manually?

And ideas, tips, instructions would be appreciated.