turn into/turn in to
Probably out of simple absentmindedness, an amazing number of Web pages of educational institutions call for people to fill out a form and “turn it into” some office or official. “Turn into” means “transform into.” Your fairy godmother can turn a pumpkin into a coach.
The way to instruct someone to submit a document is “turn in to,” with a space between the “in” and the “to”: “turn your application in to the registrar.”
Once you have your coach, you can turn into a driveway: but you cannot turn a form into a registrar unless you have very advanced origami skills.