The cancellation policy is included in the disclosures at the first session. 
For your continuing reference, it is listed here as well.

Missed Appointments:

Cancellations of scheduled appointments must be arranged with at least 24 hours notice, or they are considered “missed” sessions. In the case of a medical emergency, this policy may not apply.

Privately paying clients will be billed the full amount of the missed session.
When a third-party payer is involved, three missed sessions will constitute the end of therapy,
and the client will be referred back to the referral source for all future mental health services. 
 
In Case of Illness:

If the client has not gone to school (or work) because of illness, please reschedule the therapy appointment with as much notice as possible.