Medicare Part A

Payroll taxes paid by employers and employees on earnings — Part A is funded through the Medicare payroll tax — a percentage of earnings withheld from workers and matched by employers — deposited into the Hospital Insurance Trust Fund. That funding structure is why eligibility for premium-free Part A is tied to a person's (or their spouse's) history of Medicare-covered employment measured in quarters of coverage. Part B and Part D, by contrast, rely on beneficiary premiums and general tax revenues. This payroll-tax engine explains the credits-based eligibility rules and distinguishes Part A from the premium-funded parts of Medicare.

National insurance concept

Physician and surgeon fees for services during a hospital stay — Part A covers the institutional side of inpatient care — semi-private room and board, nursing services, hospital lab work, and supplies during the stay — but it does not cover physician and surgeon fees. Those professional services are billed under Medicare Part B, which pays 80% of the approved amount after the Part B deductible. The Part A/Part B division of labor, institutional versus professional, is a foundational Medicare structure. A beneficiary hospitalized under Part A still receives separate Part B bills from the doctors who treated them, which is a classic cause of confusion the exam tests directly.

National insurance concept