I've had referrals that consisted of my old T giving me a name & ph# scribbled on a torn page. Other referrals included handing over my entire case file, plus 1 or 2 sessions with both therapists.

You'd have to sign a release before old T could release any patient case information to new T. This would cover any case notes & assessments, e.g., if you were a threat to yourself or to others.

I have no idea whether this would include financial info, such as whether you paid on time or not.