Is there a way to file taxes for my grown son who is in jail? Not as a dependent, just to help him. He doesn't remember his pin, etc.

I am NOT trying to claim as a dependent. Just want to help him out so that taxes are filed before he gets out in two months. I know I CAN'T have the money put into my account, I just want to get them going for him. He does not remember his pin. Is there a form that can authorize me to do his taxes for him, since I'm not a firm or licensed tax agent? Please note that I cannot send him anything to sign, as the jail won't accept anything printed. So, are there alternatives, or must he wait until he is out? Thank you for any help!