	Introduction

Medicare is a federal program that pays for covered health care services of qualified beneficiaries. It was established in 1965 under Title XVIII of the Social Security Act to provide health insurance to individuals 65 and older, and has been expanded over the years to include permanently disabled individuals under 65. The program is administered by the Centers for Medicare & Medicaid Services (CMS), within the U.S. Department of Health and Human Services (HHS). In 2019, the program will cover an estimated 61 million persons (52 million aged and 9 million disabled). Medicare is required to pay for all covered services provided to eligible persons, so long as specific criteria are met. Spending under the program (except for a portion of administrative costs) is considered mandatory spending and is not subject to the appropriations process. Medicare is expected to be a high-priority issue in the current Congress. Projections of future Medicare expenditures and funding indicate that the program will place increasing financial demands on the federal budget and on beneficiaries. In response to these concerns, Congress may consider a range of Medicare reform options, from making changes within the current structure, including modifying provider payments and revising existing oversight and regulatory mechanisms, to restructuring the entire program. In the ensuing years, Medicare has undergone considerable change. P.L. The Patient Protection and Affordable Care Act (ACA; P.L. Included in the ACA, as amended, are provisions that (1) constrain Medicare's annual payment increases for certain providers; (2) change payment rates in the MA program so that they more closely resemble those in fee-for-service; (3) reduce payments to hospitals that serve a large number of low-income patients; (4) create an Independent Payment Advisory Board (IPAB) to make recommendations to adjust Medicare payment rates; (5) phase out the Part D prescription drug benefit "doughnut hole"; (6) increase resources and enhance activities to prevent fraud and abuse; and (7) provide incentives to increase the quality and efficiency of care, such as creating value-based purchasing programs for certain types of providers, allowing accountable care organizations (ACOs) that meet certain quality and efficiency standards to share in the savings, creating a voluntary pilot program that bundles payments for physician, hospital, and post-acute care services, and adjusting payments to hospitals for readmissions related to certain potentially preventable conditions. In the 114 th Congress, the Medicare Access and CHIP Reauthorization Act of 2015 (MACRA; P.L. 114-10 ) repealed the SGR formula for calculating updates to Medicare payment rates to physicians and other practitioners and established an alternative set of methods for determining the annual updates . Starting in 2019, the act will require that pharmaceutical manufacturers participating in Medicare Part D provide a larger discount on brand-name drugs purchased by enrollees in the coverage gap and will create a new high-income premium category under Parts B and D. 

	Eligibility and Enrollment

Most persons aged 65 or older are automatically entitled to premium-free Part A because they or their spouse paid Medicare payroll taxes for at least 40 quarters (about 10 years) on earnings covered by either the Social Security or the Railroad Retirement systems. Individuals of any age with ESRD who receive dialysis on a regular basis or a kidney transplant are generally eligible for Medicare. Parts A and B

Home health services and services for individuals with end-stage renal disease are covered under both Parts A and B of Medicare. The program generally pays 80% of the approved amount (most commonly, a fee schedule or other predetermined amount) for covered services in excess of the annual deductible ($185 in 2019). CMS also contracts with various private entities, including private health insurance companies, to help administer the program. Financing

Medicare's financial operations are accounted for through two trust funds maintained by the Department of the Treasury—the Hospital Insurance (HI) trust fund for Part A and the Supplementary Medical Insurance (SMI) trust fund for Parts B and D. For beneficiaries enrolled in Medicare Advantage (Part C), payments are made on their behalf in appropriate portions from the HI and SMI trust funds. Coverage may be provided through a current or former employer.
Medicare is a federal program that pays for covered health care services of qualified beneficiaries. It was established in 1965 under Title XVIII of the Social Security Act to provide health insurance to individuals 65 and older, and has been expanded over the years to include permanently disabled individuals under the age of 65. Medicare, which consists of four parts (A-D), covers hospitalizations, physician services, prescription drugs, skilled nursing facility care, home health visits, and hospice care, among other services. Generally, individuals are eligible for Medicare if they or their spouse worked for at least 40 quarters in Medicare-covered employment, are 65 years old, and are a citizen or permanent resident of the United States. Individuals may also qualify for coverage if they are a younger person who cannot work because they have a medical condition that is expected to last at least one year or result in death, or have end-stage renal disease (permanent kidney failure requiring dialysis or transplant). The program is administered by the Centers for Medicare & Medicaid Services (CMS) within the Department of Health and Human Services (HHS) and by private entities that contract with CMS to provide claims processing, auditing, and quality oversight services.
In FY2019, the program is expected to cover approximately 61 million persons (52 million aged and 9 million disabled) at a total cost of about $772 billion. Spending under the program (except for a portion of administrative costs) is considered mandatory spending and is not subject to the annual appropriations process. Services provided under Parts A and B (also referred to as "original" or "traditional" Medicare) are generally paid directly by the government on a "fee-for-service" basis, using different prospective payment systems or fee schedules. Under Parts C and D, private insurers are paid a monthly "capitated" amount to provide enrollees with required benefits. Medicare is required to pay for all covered services provided to eligible persons, so long as specific criteria are met.
Since 1965, the Medicare program has undergone considerable change. For example, during the 111th Congress, the Patient Protection and Affordable Care Act (ACA; P.L. 111-148 and P.L. 111-152) made numerous changes to the Medicare program that modified provider reimbursements, provided incentives to increase the quality and efficiency of care, and enhanced certain Medicare benefits. In the 114th Congress, the Medicare Access and CHIP Reauthorization Act of 2015 (MACRA; P.L. 114-10) changed the method for calculating updates to Medicare payment rates to physicians and altered how physicians and other practitioners will be paid in the future.
Projections of future Medicare expenditures and funding indicate that the program will place increasing financial demands on the federal budget and on beneficiaries. For example, the Hospital Insurance (Part A) trust fund is projected to become insolvent in 2026. Additionally, although the Supplementary Medical Insurance (Parts B and D) trust fund is financed in large part through federal general revenues and cannot become insolvent, associated spending growth is expected to put increasing strains on the country's competing spending priorities. As such, Medicare is expected to be a high-priority issue in the current Congress, and Congress may consider a variety of Medicare reform options ranging from further modifications of provider payment mechanisms to redesigning the entire program.
This report provides a general overview of the Medicare program including descriptions of the program's history, eligibility criteria, covered services, provider payment systems, and program administration and financing. A list of commonly used acronyms, as well as information on beneficiary cost sharing, may be found in the appendixes.