Final answer:
The patient's signed consent for release of information should always be included when sending a fax from a medical office.
Step-by-step explanation:
When sending a fax originating from a medical office, the form that should always be included is the Patient's signed consent for release of information. This form ensures that the medical office has obtained the patient's permission to share their medical records with the recipient of the fax. It is important to respect patient confidentiality and privacy, and the signed consent form helps to protect this.