How Do Social Security and Medicare Work Together?

6-minute read

Andy Markowitz,

AARP

Reviewed by

Jammie Lyell, M.S.

Published September 16, 2025

You probably know that Social Security and Medicare intersect in some ways, but you might not be clear on exactly what.

Their relationship can be confusing because they are distinct programs. Yet Social Security and Medicare both serve older and disabled Americans.

Here is the crucial connection: Social Security handles enrollment for Medicare Part A hospital insurance and Part B medical insurance.

In this role, the Social Security Administration (SSA) works with the Centers for Medicare & Medicaid Services (CMS) to inform older Americans about their Medicare sign-up options, process their applications and collect some premiums.

Early retirees receive Medicare cards via Social Security

Social Security is involved no matter when or how you enroll in Medicare.

If you’re already receiving Social Security retirement benefits at least four months before you turn 65, the SSA will send you a Welcome to Medicare package that includes your Medicare card at the start of your initial enrollment period, which begins three months before the month you turn 65. For example, if your 65th birthday is July 15, 2025, this period begins April 1.

On your 65th birthday, you’ll automatically be enrolled in parts A and B. You have the right to opt out of Part B, but you might face a penalty in the form of permanently higher premiums if you sign up for it later.

If your spouse is still working at a company with 20 or more employees and you get your health insurance that way, you can stay on your spouse’s plan until that coverage ends and save on Part B premium costs. But because you’ll get your Medicare card automatically as a retiree, you’ll need to follow the instructions in your Welcome to Medicare packet if you don’t want to keep Part B.

Don’t remove the card from the form you got in the mail. Check the box on the top right of the back of the form after “I DON’T want Part B (Medical Insurance),” sign your name and send back the entire form, including the card, in the enclosed envelope before the coverage start date on the front of the card.

Before you send it back, jot down your Medicare number so you’ll have it until you receive a new card in the mail from Social Security designating that you have only Part A.

65 and not retired? Apply for Medicare at SSA.gov

If you haven’t filed for Social Security benefits at least four months before age 65, you’ll need to apply for Medicare yourself.

You can do so any time during Medicare’s initial enrollment period, which lasts seven months. For that July 15 birthday, the sign-up window runs April 1 through Oct. 31. If you don’t enroll during that period, you could face those late fees if you do so in the future.

You don’t have to sign up during your initial enrollment period if you or your spouse:

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Are still working
Paid Medicare taxes for 40 quarters
Have private health insurance
Expect to continue working in the near future

You’ll probably want to get Part A because it’s free after 40 quarters of work and can be a secondary hospital insurance to your private plan — unless you’re eligible for a health savings account and want to continue to contribute. But you can sign up at any time.

And you’ll be eligible for a special enrollment period later for Part B when your company-based insurance ends.

Once again, the Social Security Administration is at the center of the process. You’ll find comprehensive enrollment information in SSA’s Medicare booklet and links to application forms on the Social Security website.

How Medicare premiums are paid

If you are drawing Social Security benefits, your Medicare Part B premiums are deducted from your monthly payments. If you’re not getting benefits, you’ll receive bills from CMS.

Almost all Medicare beneficiaries pay no premiums for Part A because they worked and paid their 1.45 percent Medicare tax for 40 quarters, long enough to qualify for the program.

The standard Part B premium that most Medicare enrollees pay in 2025 is $185 a month. Also in 2025, the rate rises with a beneficiary’s income, going up in steps for individuals with incomes greater than $106,000 and married couples who file taxes jointly and have a combined income of more than $212,000.

And, yes, the Social Security Administration determines whether you will pay a higher premium based on income information it receives from the IRS.

Social Security–Medicare connection started in 1965

The relationship between Social Security and Medicare is rooted in history and reflected in the title of the legislation President Lyndon Johnson signed July 30, 1965, to create Medicare. It was called the Social Security Amendments Act of 1965.

The SSA spent the following year detailing a plan for starting the program, which officially began July 1, 1966.

More than 19 million people enrolled. Today nearly 70 million benefit from Medicare, and about 9 in 10 are 65 or older.

Social Security manages SSDI and SSI, too

Medicare is not the only program distinct from retirement that SSA manages. It plays a similar administrative role with Social Security Disability Insurance (SSDI) and Supplemental Security Income (SSI).

SSDI is part of the Social Security program. It started in 1956 when Social Security’s rules were amended to permit benefits for disabled workers.

Social Security Disability Insurance is an earned benefit. As with Social Security retirement benefits, you qualify by working and paying Social Security taxes. However, unlike with retirement benefits, you can qualify for SSDI at any age.

For your SSDI application to be approved, you must demonstrate severe or total disability: an injury or condition that prevents you from engaging in “substantial gainful activity,” meaning most work, and is expected to last at least one year or result in death. Social Security maintains a detailed list of impairments with additional information on how it evaluates disability claims.

If the agency approves your disability claim, your payment is calculated as if you had reached full retirement age. That’s the age at which you can receive 100 percent of the benefit you are entitled to, based on your earnings history.

Social Security also manages the Supplemental Security Income program and disburses monthly benefits to recipients; however, money for SSI does not come from payroll taxes. U.S. Treasury general revenues primarily finance SSI benefits.

To qualify for SSI, you must be at least 65 years old, blind or have a disability. Beyond that basic requirement, Social Security has a complex formula for determining what income and assets factor into SSI eligibility.

This story, originally published Feb. 19, 2020, was updated with additional information and a graphic.

Get Started With Medicare, Centers for Medicare & Medicaid Services
Plan for Medicare, Social Security Administration
Medicare booklet, Social Security Administration
Get Ready for Medicare package (automatically enrolled), Medicare.gov
How to drop Part A & Part B, Medicare.gov
New Medicare Card Project, Centers for Medicare & Medicaid Services
Original Medicare (Part A and B) Eligibility and Enrollment, Centers for Medicare & Medicaid Services
When to sign up for Medicare and Sign Up for Medicare, Social Security Administration
Special Enrollment Periods for Part A & Part B, Medicare.gov
Topic No. 751, Social Security and Medicare Withholding Rates, IRS
Premiums: Rules for Higher-Income Beneficiaries, Social Security Administration
Fact sheet: 2025 Medicare costs, Medicare.gov
Report on the Implementation of the 1965 Amendments, Social Security Administration
Medicare Monthly Enrollment, May 2025, Centers for Medicare & Medicaid Services
Disability, Social Security Administration
Fact Sheet: Social Security Disability Insurance (SSDI), Social Security Administration
Disability Benefits: How Does Someone Become Eligible, Social Security Administration
Supplemental Security Income (SSI) Overview, Social Security Administration
Social Security Disability Insurance (SSDI) and Supplemental Security Income (SSI): Eligibility, Benefits, and Financing, Congressional Research Service

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Andy Markowitz is an AARP senior writer and editor covering Social Security and retirement. He is a former editor of the Prague Post and Baltimore City Paper.

Jammie Lyell is the Social Security program manager for AARP's office of community, state and national affairs. He formerly worked at the Social Security Administration as a legal administrative specialist and technical expert.