Do I need to formally leave the school I'm transferring from?

So here’s the situation. I attended my old school (a CSU) for two years, left, and am now enrolled at my local community college taking classes to prep me to transfer to a different institution. Currently, I’m on a “leave of absence” at my CSU but it’ll end after spring 2018.

I plan to enroll at a new university by the end of May, or at least submit my SIR to do so. Is that allowed? Can I enroll at a new school without worrying about my CSU?

There is a form to “withdraw” from my CSU, but I’d have to turn it in in person and visit my assigned advisor to certify I’m allowed to withdraw. Do I need to do that?

Thanks in advance, everyone!

I have no direct experience with UCs or CSUs but it is a good habit to follow whatever the documented process is. Especially if you will need transcripts from the CSU to be sent to your new institution. You don’t want those transcripts to say “Unofficial Withdrawal” or some such thing.