Which billing terms apply to ER observation stays vs inpatient admissions?

• A. Observation = Part A; Inpatient = Part B
• B. Observation = Part B; Inpatient = Part A
• C. Observation = Private Insurance; Inpatient = Medicare Part A
• D. Observation = Medicare Part A; Inpatient = Private Insurance

Answer: (B)

In Medicare billing, observation stays are treated as outpatient services and are billed to Part B, while an actual inpatient admission is billed under Part A. This distinction matters because Part A covers inpatient hospital care with its own deductible and coinsurance, whereas Part B covers outpatient services (like observation) with a separate deductible and coinsurance. Also, time in observation does not count toward the inpatient days needed for certain benefits (for example, some SNF coverage requires a formal inpatient stay of at least 3 days). Therefore, the correct pairing is observation billed to Part B and inpatient billed to Part A.