A doctor needs the fax number of a pharmacy so that he can send the original prescription directly in for processing, according to National Prescription Services. While patients can deliver original prescriptions in person or through the mail, they may not fax them.
When a doctor faxes in a prescription, he must include a cover sheet from his office. This policy applies both to retail and mail-order pharmacies. The reason for this requirement is that pharmacy pads have security features in some states, notes the Indiana Professional Licensing Agency. Faxes remove access to those features, which is why pharmacists cannot accept faxes from any other source than the prescribing doctor's office.