Final answer:
The reimbursement methodology for inpatient psychiatric facility services payment system is Per Diem.
Step-by-step explanation:
The reimbursement methodology for inpatient psychiatric facility services payment system is Per Diem.
Per Diem payment system is when a specific payment rate is established for each day of the admission.
Reference: Stensland, M., Watson, P. R., & Grazier, K. L. (2012). An examination of costs, charges, and payments for inpatient psychiatric treatment in community hospitals. Psychiatric Services, 63(7), 66-71.