Stabilizing Medicare Access to Rehabilitation and Therapy Act or the SMART Act This bill modifies the application of a certain Medicare payment methodology for outpatient physical therapy services and outpatient occupational therapy services that are furnished by a therapy assistant. Under current law, effective January 1, 2022, payment for such services is 85% of the otherwise applicable rate. The bill delays this effective date by one year and excludes services that are furnished in rural or medically underserved areas from this payment methodology. The bill also specifies that supervision requirements for outpatient physical therapy services that are furnished through private practice may not be more stringent for purposes of Medicare coverage than under state law.