At D26’s school, she submits an application, prints out proof of submission (confirmation page from common app or an email or something), then attaches it to a physical form with basic info – did she apply EA or ED, the deadline, which college/dept, etc.
Her school requests this to be turned in to college advising office two weeks ahead of the college’s deadline, and they make every effort to send it within the first week of getting it.
I’m not entirely sure what happens if they don’t. I think most colleges have a grace period after the deadline to get all documents in?
Georgia Tech, for example, has an EA deadline of October 15 (for in-state students), but document deadline of October 31. And they list November 15 for self-reported test score deadline because they want to give students a chance to take a fall test.