An SAO Fee Waiver waives the application fee to the specific school that issued it to you. It will not waive the application fee to any other school nor does it waive SSAT, Snapshot or other fees.
An SAO Fee Waiver does also waive the $10 SAO administrative fee for that school's application, however, it will not waive the $10 administrative fee for any other schools.
To see if you are eligible for an SAO Fee Waiver, contact the school or schools to which you are applying. Each school sets their own eligibility, policies, or rules for SAO Fee Waiver eligibility and some schools may not offer SAO Fee Waivers.
SAO Fee Waivers may not be applied after an application has already been paid.