From the AACOMAS FAQ:
How do I send my official MCAT scores to AACOMAS?
A: MCAT scores must be sent electronically from MCAT in order to be considered official. You can log into your MCAT account via the MCAT Testing History (THx) System and have your scores released to AACOMAS. Scores are sent to AACOMAS using your social security number as identification. If you do not wish to list your social security number on the AACOMAS application, please have MCAT provide you with a new nine-digit number and list that number on the AACOMAS application.