HCPCS S9131: Physical Therapy, In-Home Per Diem
HCPCS Level II code S9131 designates physical therapy services provided in the home on a per diem basis. This code is used to capture home-based physical therapy encounters where reimbursement is structured as a daily rate rather than per unit time or individual procedure. Nationally, home-based therapy codes like S9131 are important for documenting care delivered outside institutional settings and for aligning payment with delivery models that emphasize functional recovery and reduced hospital utilization.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the code's clinical context, typical diagnoses that prompt home physical therapy, commonly related procedural codes used to describe specific interventions, and the payer landscape relevant to this service. The publication also provides benchmarking and policy context where available, notes common billing modifiers and associated provider taxonomies, and summarizes related CPT/HCPCS services often billed alongside home-based physical therapy.
This summary is intended for clinicians, billing professionals, and policy analysts seeking a clear national-level description of S9131, its clinical role in home care, and the payer framework that governs its use.
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Billing Code Overview
HCPCS Level II code S9131 represents physical therapy delivered in the patient's home on a per diem basis. The service type is physical therapy, and the typical site of service is the patient's home (home health/home-based care). This code denotes a daily payment for provision of physical therapy services provided in the home setting.
National Reimbursement Benchmarks
Commercial rates for HCPCS S9131 cluster around BUCA’s average commercial benchmark of $102.30, while individual payer distributions display meaningful divergence. Blue Cross Blue Shield (BCBS) shows the highest upper-bound volatility with a P75−P25 interquartile range of $48.10 ($132.50 − $84.40), reflecting a wide spread in typical paid levels; Aetna is much tighter with an IQR of $3.00 ($77.00 − $74.00). UnitedHealth Group has an unusual profile with a P25 of $0.00 and P75 of $122.00, producing an IQR of $122.00 driven by zero-value observations and a high median at $115.00.
Cigna and BUCA sit between these extremes: Cigna’s IQR is effectively $0.00 ($97.90 − $97.90), indicating highly concentrated common payments, while BUCA’s IQR is $63.60 ($118.10 − $75.50), showing moderate dispersion around its $102.30 mean. Overall, payers range from very concentrated typical rates (Cigna, Aetna) to wide variability (UnitedHealth Group, BCBS, BUCA), which affects predictability of reimbursement for this code.