Prior Authorization Forms Certain medications may need approval from your insurance carrier before they are covered. A Prior Authorization Form must be submitted if the prescribed medication requires approval. Follow these simple steps in order to complete and submit a Prior Authorization form for review. 3 Easy Steps Step 1 Patient completes Part A. Step 2 Prescribing physician completes Part B. Step 3 Fax or mail the completed form to Express Scripts Canada®. Fax Express Scripts Canada Clinical Services 1 (855) 712-6329 Mail Express Scripts Canada Clinical Services 5770 Hurontario Street, 10th Floor, Mississauga, ON L5R 3G5