Medicare Part B starts automatically when you turn 65 or after you receive SSDI for 24 months

If you are receiving SSDI, Medicare Part B enrollment happens without you filing a separate form. The Social Security Administration (SSA) registers you automatically once you meet the time requirement. For most people on SSDI, that means Part B coverage begins the first day of the month you turn 65. If you are already 65 when you start SSDI, Part B begins 24 months after your SSDI award date.

Part B covers doctor visits, outpatient care, lab work, X-rays, and durable medical equipment like wheelchairs or oxygen. It does not cover hospital stays — that is Part A, which you also receive automatically. The automatic enrollment means you do not have to worry about missing a important date, but it also means you will owe premiums whether you use the benefits or not.

Key Takeaways

  • Part B enrollment is automatic at age 65 or 24 months after your SSDI award, with no action required on your part.
  • Part B premiums are deducted directly from your SSDI check each month, and the amount changes yearly based on your income from two years prior.
  • If your income is below a certain threshold, you may pay a standard premium; higher earners pay an income-related surcharge called IRMAA on top of the base amount.
  • You can decline Part B coverage during your initial enrollment period, but doing so may result in a permanent penalty if you enroll later.
  • Part B works alongside SSDI but is a separate Medicare program with its own rules, deductibles, and copayments.

How Part B premiums are calculated and deducted from your SSDI payment

Your Part B premium comes out of your SSDI benefit each month. The base premium amount changes every January and is set by Medicare based on the cost of providing the benefit. For 2024, the standard premium is $164.90 per month, but this figure changes annually. SSA deducts the premium before depositing your SSDI payment to your bank account, so you never see that money.

If your income from two years ago was above a certain level, you pay more than the standard premium through a surcharge called Income-Related Monthly Adjustment Amount (IRMAA). For example, if your 2022 income was above $91,000 (for a single filer), you would have paid a higher premium in 2024. The income threshold changes each year, and SSA uses your tax return to calculate it. You will receive a notice in the mail showing your premium amount and the income figure SSA used.

If you believe SSA used the wrong income year — for instance, you had a one-time payment or your income dropped significantly — you can request a recalculation. This is called a life-changing event appeal, and you have 60 days from the date on your premium notice to file it with SSA.

What happens if your income changes after enrollment

Medicare uses your tax return from two years prior to set your premium. If your income drops sharply — you stop working, your investment income falls, or you have a major life event — your premium may not reflect your current situation. You can file an appeal with SSA to have your premium recalculated based on your current year's income instead.

Life-changing events that SSA recognizes include loss of employment, reduction in work hours, loss of income-producing property, death of a spouse, divorce, or a significant drop in pension or investment income. You will need to provide documentation: a letter from your employer showing the job loss, a copy of your current tax return, or a divorce decree, depending on the event. SSA processes these appeals and notifies Medicare of any change, which then adjusts your premium going forward.

If you do not report a change and your income has actually risen, Medicare may later bill you for back premiums. The reverse is also true: if your income fell and you did not report it, you may have overpaid, and SSA can issue a refund or credit to your account.

The difference between Part B and Part A, and why you need both

Part A covers inpatient hospital care, skilled nursing facility stays, hospice, and home health services. Part B covers outpatient services: doctor office visits, preventive care, lab work, imaging, and equipment. You receive both automatically when you turn 65 or after 24 months on SSDI. Part A has no premium for most people because you or your spouse paid Medicare taxes while working. Part B has a monthly premium that comes from your SSDI check.

Together, they form Original Medicare, which is different from Medicare Advantage (Part C) or prescription drug coverage (Part D). If you enroll in Part B, you can also choose to add Part D through a separate plan, which covers prescription medications. Some people on SSDI choose to join a Medicare Advantage plan instead of staying in Original Medicare, but that is a separate decision made during the annual enrollment period.

Declining Part B and the permanent penalty for late enrollment

You have the right to turn down Part B when you first become may be able to access. This is called declining coverage during your initial enrollment period. If you are working and have health coverage through your employer, you might choose to decline Part B to avoid paying the premium. However, if you decline and later want to enroll, you will face a permanent penalty.

The Part B late enrollment penalty is 10 percent of the standard premium for each 12-month period you were may be able to access but not enrolled. If you declined at age 65 and did not enroll until age 70, that is five years of penalty — 50 percent added to your premium for life. The penalty does not go away, even if you later change your mind. The only exception is if you had creditable coverage (health insurance through an employer or union) during the time you were not enrolled in Part B. If you had that coverage, you can enroll without penalty during the eight-month period after your coverage ends.

If you are still working when you turn 65 and have employer health coverage, contact SSA before declining Part B. Ask about the rules for your specific situation, because the penalty rules have exceptions, and getting it wrong is costly.

How Part B works with Medicaid when you are on SSDI

If your SSDI payment is low enough, you may also be enrolled in Medicaid, which is a separate program run by your state. Medicaid can cover costs that Medicare does not: dental, vision, hearing aids, and long-term care. When you have both Medicare and Medicaid, Medicaid is called your secondary payer, meaning Medicare pays first and Medicaid covers what Medicare does not.

Some states have programs that pay your Part B premium for you if your income is below a certain level. These are called may have access to Medicare Beneficiary (QMB) programs or Specified Low-Income Medicare Beneficiary (SLMB) programs. Your state Medicaid office determines whether you may have access to. If you do, Medicaid sends the premium directly to Medicare on your behalf, so it does not come out of your SSDI check. You still receive the full SSDI amount.

To learn about your state has a premium-payment program, contact your state Medicaid office or call 1-800-MEDICARE. They can tell you the income limits and what documents you need to provide.

Part B deductibles, copayments, and what you actually pay when you see a doctor

Part B has an annual deductible, which changes each year. For 2024, the deductible is $240. This means you pay the first $240 of your Part B services out of your own pocket before Medicare starts paying its share. After you meet the deductible, Medicare typically pays 80 percent of the approved amount for most services, and you pay 20 percent.

However, some services are covered at 100 percent with no copayment: preventive care like annual wellness visits, cancer screenings, and vaccinations. Your doctor's office should tell you before your visit whether a service is preventive or will count toward your deductible. If you are unsure, call the office ahead of time and ask.

If your doctor does not accept Medicare assignment — meaning they do not agree to accept Medicare's approved amount as full payment — you could owe more than the 20 percent copayment. This is called balance billing. Before scheduling an appointment, confirm that your doctor accepts Medicare assignment. You can search for doctors on Medicare.gov or call your doctor's office directly.

Frequently Asked Questions

Can I delay Part B enrollment if I am still working when I turn 65?

Yes, if you have health coverage through your employer or union. You can decline Part B without penalty as long as you enroll within eight months after your coverage ends or you stop working, whichever comes first. Contact SSA before you decline to make sure your employer coverage qualifies as creditable coverage under Medicare rules.

What if I move to another state after I start receiving SSDI and Part B?

Your SSDI and Part B coverage continue regardless of where you live. However, your Medicaid coverage may change because Medicaid rules vary by state. Contact your new state's Medicaid office to find out whether you remain enrolled and what your benefits are. Your Part B premium and Medicare coverage stay the same.

Do I have to pay Part B premiums if I am not using Medicare?

Yes. Once you are enrolled in Part B, you pay the monthly premium whether you use the benefits or not. The only way to stop paying is to disenroll, but doing so after your initial enrollment period triggers the permanent late-enrollment penalty. If you are not using Medicare and want to disenroll, contact SSA or Medicare to discuss your options before you make a decision.

Can Part B premiums increase if my SSDI payment is very small?

No. There is a hold-harmless rule that prevents your SSDI payment from decreasing because of a Part B premium increase. If your premium goes up and would reduce your SSDI check below what you received the previous month, SSA freezes your premium at the previous amount. However, this protection applies only to the base premium, not to IRMAA surcharges for higher-income beneficiaries.

What if I disagree with the income figure Medicare used to calculate my IRMAA?

You can request a recalculation by filing a life-changing event appeal with SSA within 60 days of receiving your premium notice. You will need to provide documentation of the event that changed your income, such as a termination letter, current tax return, or divorce decree. SSA reviews the appeal and notifies Medicare of any change.