Medicare enrollment periods: when you can sign up or switch
Most people first sign up during the 7-month Initial Enrollment Period: 3 months before the month they turn 65, that month, and 3 months after. If you're covered by a current job's plan, you get an 8-month Special Enrollment Period after the job or coverage ends. Once you have Medicare, you can change Medicare Advantage or Part D plans each year from October 15 to December 7, and if you're in Medicare Advantage you get one more chance to switch from January 1 to March 31. Missing a window can mean coverage gaps and lifelong penalties.
All the Medicare enrollment windows
| Period | When | What you can do |
|---|---|---|
| Initial Enrollment Period | 7 months: starts 3 months before the month you turn 65, ends 3 months after | Sign up for Part A and Part B; join a Medicare Advantage or Part D plan |
| Part B Special Enrollment Period (working past 65) | While covered by a current employer plan (yours or your spouse's), or within 8 months after the job or that coverage ends, whichever is first | Sign up for Part B (and Part A) without a late penalty |
| Medicare Open Enrollment Period | October 15 – December 7 each year (coverage starts January 1) | Join, switch or drop Medicare Advantage or Part D plans; move between Original Medicare and Medicare Advantage |
| Medicare Advantage Open Enrollment Period | January 1 – March 31 each year (or within your first 3 months of Medicare), only if you're in a Medicare Advantage plan | Switch to another Medicare Advantage plan, or drop it and return to Original Medicare (and join a drug plan) |
| Medigap Open Enrollment Period | 6 months, starting the first month you're 65+ and have Part B | Buy any Medigap policy sold in your state without health questions affecting eligibility or price |
| Special Enrollment Periods | Varies, after events like moving, losing coverage, getting Medicaid or Extra Help | Join or switch Medicare Advantage or drug plans |
| General Enrollment Period | January 1 – March 31 each year | Sign up for Part A and/or Part B if you missed your earlier chances; coverage starts the month after you sign up, and late penalties may apply |
Sources: Medicare.gov, Joining a plan and When can I sign up for Medicare?, last reviewed October 28, 2026.
Do you have to sign up at 65?
If you already get Social Security retirement benefits, you're usually enrolled in Parts A and B automatically. Otherwise you sign up through Social Security. Whether you should delay Part B depends on your other coverage:
- Coverage from a current job (yours or your spouse's): Medicare.gov notes you may be able to wait and use the 8-month Special Enrollment Period, but if the employer has fewer than 20 employees, your job-based plan might not pay unless you have Parts A and B. Check with the employer.
- COBRA or retiree coverage: doesn't count as current employment. Your 8-month window starts when you stop working, even if you take COBRA.
- Marketplace coverage: once you're eligible for premium-free Part A, you can't keep getting Marketplace premium savings, and your Marketplace plan may not renew. Plan the switch.
- HSA: you can't contribute to an HSA once enrolled in Medicare. See HSA basics.
Penalties to avoid
- Part B late penalty: a monthly penalty that goes up the longer you wait, generally for as long as you have Part B, if you don't sign up when first eligible and don't qualify for a Special Enrollment Period.
- Part D late penalty: applies if you go 63 days or more without Part D or other creditable drug coverage after you're first eligible.
New to the choices? Start with Medicare basics.
Frequently asked questions
When can I first sign up for Medicare?
During your 7-month Initial Enrollment Period, which starts 3 months before the month you turn 65 and ends 3 months after it.
When is Medicare Open Enrollment?
October 15 to December 7 each year. Changes take effect January 1.
Can I switch Medicare Advantage plans after January 1?
Yes, if you're already in a Medicare Advantage plan you can switch plans or return to Original Medicare once during the Medicare Advantage Open Enrollment Period, January 1 to March 31.
Does COBRA let me delay Part B without a penalty?
No. COBRA isn't coverage based on current employment. Your 8-month Special Enrollment Period starts when you stop working, even if you choose COBRA.
What if I missed my Initial Enrollment Period?
You can sign up during the General Enrollment Period, January 1 to March 31, with coverage starting the month after you sign up, but you may pay late enrollment penalties.
Sources
- Medicare.gov: Joining a plan (enrollment periods) (accessed October 28, 2026)
- Medicare.gov: When can I sign up for Medicare? (accessed October 28, 2026)
- Medicare.gov: Your coverage options (accessed October 28, 2026)
- Medicare.gov: When can I buy a Medigap policy? (accessed October 28, 2026)
- SHIP National Technical Assistance Center: find your State Health Insurance Assistance Program (accessed October 28, 2026)