I Have Medicare Part A but Not Part B. Can I Buy a Marketplace Plan?

Short answer: In most cases, no. Medicare Part A counts as Medicare, even if you never signed up for Part B. If your Part A is premium-free, you can't get premium tax credits on the Marketplace (HealthCare.gov or your state exchange), and it is against federal law for an agent or insurance company that knows you have Medicare to sell you a Marketplace or other individual health plan. The one exception: if you pay a monthly premium for Part A, you can drop Part A (and Part B, if you have it) and enroll in a Marketplace plan, with subsidies if your income qualifies.

For most people with Part A only, the better fix is to enroll in Medicare Part B, then add a Medicare Supplement (Medigap) or Medicare Advantage plan and a Part D drug plan. Here is how it works.

Why can't I buy a Marketplace plan if I only have Part A?

There are three separate rules that apply.

• Part A is minimum essential coverage. Enrollment in Part A counts as qualifying health coverage under the Affordable Care Act, whether or not you have Part B.
• No subsidies with premium-free Part A. Anyone eligible for or enrolled in premium-free Part A is not eligible for advance premium tax credits or cost-sharing reductions. A Marketplace plan would cost full price.
• The anti-duplication law. Section 1882(d) of the Social Security Act makes it illegal to knowingly sell someone with Medicare a health policy that duplicates Medicare benefits. That covers Marketplace plans and individual plans sold off the exchange.

If you were already on a Marketplace plan before your Medicare started, you are allowed to keep it, but your tax credits end once your premium-free Part A starts. See Can I Get Obamacare if I Qualify for Medicare?

Does it matter if I don't have Part B?

No. Marketplace eligibility depends on Part A, not Part B. Skipping Part B does not make you eligible for a Marketplace plan or subsidies. It just leaves you without coverage for doctor visits, outpatient care, lab work, and other Part B services. Part A covers mainly hospital inpatient care, skilled nursing, hospice, and some home health care.

When can I buy a Marketplace plan with Part A?

Only if you pay a premium for Part A, which usually means you (or your spouse) worked fewer than 40 quarters (about 10 years) in Medicare-covered jobs. In 2026, premium Part A costs:

If you pay for Part A, you can drop it (and Part B) and enroll in a Marketplace plan during Open Enrollment or a Special Enrollment Period. Depending on your income, a subsidized Marketplace plan can cost far less than buying into Medicare. Our full guide compares the two: I'm turning 65 but have to pay a premium for Part A. Can I sign up for a Marketplace plan instead?

Can I drop premium-free Part A to get a Marketplace plan?

Generally, no. If you receive Social Security or Railroad Retirement benefits, you can't drop premium-free Part A without also withdrawing your retirement benefits and paying back everything you have received, including any Medicare costs paid on your behalf. For almost everyone, that makes dropping Part A impractical. More detail: Can a consumer drop Medicare Part A to enroll in Marketplace coverage?

How do I sign up for Part B if I missed my first chance?

You have three possible routes.

1. General Enrollment Period (GEP): January 1 to March 31 every year. Anyone who missed their Initial Enrollment Period can sign up during this window. Coverage starts the first day of the month after you enroll. For example, sign up in January 2027 and Part B starts February 1, 2027.
2. Special Enrollment Period for job-based coverage. If you (or your spouse) are covered by a group health plan through current employment, you can sign up any time you are still covered, or within 8 months after the job or the coverage ends, whichever comes first. A Marketplace plan, COBRA, and retiree coverage do not qualify for this SEP. See When should I enroll in Medicare Part B if I have employer coverage?
3. Exceptional circumstances SEPs. Medicare also offers SEPs for situations like losing Medicaid, a natural disaster or emergency, an employer or health plan error, or incorrect information from a federal employee.

You can apply at SSA.gov, by calling Social Security at 1-800-772-1213, or at a local Social Security office. For more on enrollment windows, read When can I sign up for Medicare Parts A and B?

Is there a penalty for signing up for Part B late?

Usually, yes. Your Part B premium goes up 10% for each full 12-month period you could have had Part B but didn't, unless you had job-based coverage from current employment. You pay the penalty for as long as you have Part B. The standard 2026 Part B premium is $202.90 per month. Use our calculator in Medicare Late Enrollment Penalties: Part A, B and D Explained to estimate yours.

Waiting longer only makes the penalty bigger, so if you don't have qualifying job-based coverage, it usually makes sense to enroll in the next General Enrollment Period.

What coverage can I get with Part A only?

• Part D drug coverage: Yes. You can join a stand-alone Part D plan with Part A only.
• Medicare Advantage (Part C): No. You need both Part A and Part B.
• Medicare Supplement (Medigap): No. You need both Part A and Part B.

Good news if you enroll in Part B late: your 6-month Medigap Open Enrollment Period starts the month your Part B begins (if you are 65 or older). During that window, insurers must sell you any Medigap plan they offer at standard rates, with no health questions. See How to Compare Medigap Plans

What if I can't afford the Part B premium?

If your income and assets are limited, a Medicare Savings Program run by your state may pay your Part B premium, and sometimes your deductibles and coinsurance too. In many states, qualifying for a Medicare Savings Program also lets you enroll in Part B outside the usual windows, without a late penalty. Learn more in Medicare Savings Programs: Getting Help with Medicare Costs

Does this apply if I'm under 65 and have Part A because of a disability?

Yes. People under 65 who have premium-free Part A based on disability (SSDI) or ALS follow the same Marketplace rules: no tax credits, and agents can't sell them a duplicate individual plan. They can enroll in Part B using the same enrollment periods described above.

Quick summary

Get help from a licensed Medicare advisor

Independent Health Agents is a licensed, independent agency. We can confirm whether your Part A is premium-free, map out your next Part B enrollment window, and compare Medigap, Medicare Advantage, and Part D plans from multiple carriers at no cost to you.

Sources: HealthCare.gov, Medicare.gov, CMS Marketplace assister guidance, and Social Security Act Section 1882(d). Figures are for 2026; 2027 Part A and B premiums will be added once CMS releases them.