Medicare Part A vs Part B
Part A covers inpatient hospital, SNF, hospice, and some home health. Part B covers physician services, outpatient care, DME, and preventive services. Billing systems and claim forms differ.
Last reviewed May 24, 2026
Side by side
Medicare Part A
Hospital Insurance — covers inpatient hospital stays, skilled nursing facility care, hospice, and limited home health services.
Title XVIII Part A- Billed on UB-04 (institutional claim).
- Paid via prospective payment systems (IPPS, IRF-PPS, etc.).
- Provider enrolls via CMS-855A.
Medicare Part B
Medical Insurance — covers physician and other practitioner services, outpatient hospital, DME, lab, imaging, and preventive services.
Title XVIII Part B- Billed on CMS-1500 (professional claim).
- Paid under MPFS, OPPS (outpatient), CLFS (lab), and others.
- Provider enrolls via CMS-855B or CMS-855I.
When to use Medicare Part A
- Inpatient hospital, SNF, or hospice care — bill Part A on UB-04.
When to use Medicare Part B
- Physician office visit, outpatient procedure, lab, imaging, DME — bill Part B on CMS-1500.
Common mistakes
- Billing inpatient services on CMS-1500 (physician professional fee is Part B; the institutional fee is Part A on UB-04 — both can apply to the same admission).
- Confusing enrollment paths — a physician group needs 855B, individual physicians need 855I.
Sources
- CMS — Medicare Parts A & Bhttps://www.cms.gov/medicare
- CMS — Medicare Enrollment Applications (855)https://www.cms.gov/medicare/enrollment-renewal/providers-suppliers/enrollment-applications
Related
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This comparison is a research aid for billing and compliance staff. It does not provide legal, medical, or financial advice and does not replace counsel. References cited link to primary sources at CMS, HHS, OCR, eCFR, NIST, and the relevant payer or state regulator. Last reviewed May 24, 2026.