How Medicare enrollment periods work
Medicare has fixed windows for signing up for Part A and Part B and for joining, switching or dropping Medicare Advantage, Part D and Medigap coverage. Outside those windows you usually have to wait, and signing up late can mean a gap in coverage and a penalty that lasts as long as you have Medicare. The table below summarizes the windows; each one is explained further down.
Timeline at a glance
| Period | Dates | What you can do | When coverage starts |
|---|---|---|---|
| Initial Enrollment Period | 7 months: 3 months before your 65th birthday month, that month, and 3 months after | Sign up for Part A and Part B; join a Medicare Advantage or Part D plan | First of your birthday month if you sign up before it; otherwise the first of the month after you sign up |
| Medigap open enrollment | 6 months, starting the month you're 65 and have Part B | Buy any Medigap policy sold in Arizona with no health questions | When the policy says |
| General Enrollment Period | January 1 to March 31 | Sign up for Part A or Part B if you missed your other chances | First of the month after you sign up |
| Annual Enrollment Period | October 15 to December 7 | Join, switch or drop Medicare Advantage or Part D plans | January 1 |
| Medicare Advantage Open Enrollment Period | January 1 to March 31 | One change if you're in a Medicare Advantage plan | First of the month after the change |
| Part B Special Enrollment Period | 8 months after job-based coverage or the job ends, whichever is first | Sign up for Part B (and Part A) without a penalty | First of the month after you sign up, or up to 3 months later if you ask |
| Plan not renewing (2027 exits) | December 8, 2026 to February 28, 2027 | Choose a new Medicare Advantage or Part D plan | First of the month after you join |
Initial Enrollment Period (around age 65)
Your Initial Enrollment Period is 7 months long: the 3 months before the month you turn 65, your birthday month, and the 3 months after. If you already get Social Security retirement or Railroad Retirement benefits, you are enrolled in Part A and Part B automatically and your card arrives in the mail. If not, you sign up with Social Security online, by phone or at an Arizona Social Security office.
Sign up in the 3 months before your birthday month and coverage starts the first day of your birthday month. Sign up during or after your birthday month and coverage starts the first day of the next month. If you're still working with employer coverage, you may be able to delay Part B without a penalty; see working past 65.
People under 65 who get Social Security disability benefits are enrolled in Medicare automatically after 24 months of benefits. People with ALS get Medicare the month disability benefits begin. See Medicare eligibility.
General Enrollment Period
If you missed your Initial Enrollment Period and don't qualify for a special enrollment period, you can sign up for Part B (or Part A if you pay a premium for it) from January 1 to March 31 each year. Coverage starts the first day of the month after you sign up. You may owe a late enrollment penalty (see below).
Annual Enrollment Period: October 15 to December 7
Each fall, anyone with Medicare can join, switch or drop a Medicare Advantage plan or a Part D drug plan, or move between Original Medicare and Medicare Advantage. Your choice takes effect January 1. The window open now covers 2027.
Before it starts, your plan sends an Annual Notice of Change listing next year's changes. Read it even if you're happy with your plan: premiums, networks, drug lists and service areas can all change. If you make more than one change during the period, the last one you make before December 7 counts.
Medicare Advantage Open Enrollment Period: January 1 to March 31
If you are in a Medicare Advantage plan on January 1, you can make one change by March 31: switch to a different Medicare Advantage plan, or drop your plan, return to Original Medicare and join a Part D plan. If you are new to Medicare and joined a Medicare Advantage plan, you get the same one change during your first 3 months with Medicare. This period can't be used to move from Original Medicare into Medicare Advantage or to switch between standalone drug plans.
Special enrollment periods
Certain life events open a special enrollment period (SEP) outside the usual windows. These are the ones Arizonans use most.
Moving to, from or within Arizona
- Moving to a new address outside your plan's service area, whether into Arizona, out of it, or to an Arizona county your plan doesn't serve: you can switch plans or return to Original Medicare. The window starts the month you move (or the month before, if you tell your plan ahead of time) and lasts 2 full months after the move.
- Moving within your plan's area to a place with new plan options: you can also switch during the same kind of window.
- Returning to the U.S. after living abroad: you can join a plan during the 2 full months after the month you move back.
- Seasonal stays are not moves. Wintering in Arizona while keeping your home elsewhere doesn't create a special enrollment period. But a Medicare Advantage plan must disenroll you if you are outside its service area for more than 6 months in a row (unless it has a visitor or traveler program), and that opens a window to choose new coverage. See snowbirds and seasonal residents.
Losing employer or union coverage
When job-based coverage from your own or your spouse's current work ends, you have 8 months to sign up for Part B without a penalty, starting the month after the job or the coverage ends, whichever comes first. To join a Medicare Advantage or Part D plan, you have 2 full months after the month the coverage ends. COBRA and retiree coverage don't count as coverage from current work for the Part B rule; see working past 65.
AHCCCS and Extra Help
- Once a month, if you have AHCCCS (Arizona's Medicaid program) and Medicare, or you get Extra Help (people in a Medicare Savings Program get it automatically), you can switch to a different standalone Part D drug plan, or leave a Medicare Advantage plan with drug coverage for Original Medicare plus a standalone drug plan.
- Integrated D-SNPs: if you have Medicare and full AHCCCS benefits, you can join or switch to an integrated dual eligible special needs plan once a month, where one is offered in your area.
- Losing AHCCCS or Extra Help: you have 3 months from the later of the date you lose eligibility or the date you're notified to make one change.
Changes take effect the first day of the next month. The monthly drug-plan change isn't available to someone their plan has identified as at risk under a Part D drug management program. More on AHCCCS and Medicare and Medicare Savings Programs in Arizona.
Your plan is ending or leaving your area
When a Medicare Advantage or Part D plan doesn't renew its contract or stops serving your county, you can choose a new plan from December 8 until the last day of February. For the 2027 exits, that is through February 28, 2027, in addition to the Annual Enrollment Period. Some companies stop offering plans in some Arizona counties for 2027; if yours is one of them, see Arizona plans ending in 2027. If you don't choose, you'll be in Original Medicare on January 1 without drug coverage. You may also have a guaranteed right to buy a Medigap policy within 63 days after your plan coverage ends (see Medigap in Arizona).
Emergencies and major disasters
If a federal, state or local government declares an emergency or major disaster where you live (or where the person who helps you with health care decisions lives), and it kept you from making a change during another enrollment period you were eligible for, you get a special enrollment period for Medicare Advantage and Part D. It starts with the declaration or incident and lasts until 2 full calendar months after the incident ends. For declarations with no stated end date, the incident is treated as ending 1 year after it began unless the declaration is renewed.
Other situations
Other special enrollment periods include moving into or out of a nursing home or other institution, losing creditable drug coverage through no fault of your own, and leaving a job-based plan to join Medicare coverage. If you think something unusual kept you from enrolling, call 1-800-MEDICARE to ask whether an exceptional-circumstance period applies.
Medigap open enrollment
Your one-time Medigap open enrollment period lasts 6 months, starting the first month you are 65 or older and have Part B. During it, companies selling Medigap in Arizona must sell you a policy regardless of your health. Arizona has no birthday rule or yearly switching right, so after this period you generally need to answer health questions unless a federal guaranteed-issue right applies. Details on Medigap in Arizona.
Late enrollment penalties
Part B: if you don't sign up when first eligible and don't have job-based coverage from current work, your Part B premium can go up 10% for each full 12-month period you could have had Part B but didn't. The penalty usually lasts as long as you have Part B. The standard premium is $202.90 a month in 2026.
Part D: if you go 63 days or more in a row without Part D or other creditable drug coverage after your Initial Enrollment Period, a penalty is added to your drug plan premium: 1% of the national base beneficiary premium ($38.99 in 2026) for each full month you went without coverage. It usually lasts as long as you have Part D. People who get Extra Help don't pay it.
Estimate a penalty with our late enrollment penalty calculator.
Getting help
To see plans for your Arizona ZIP code during an open window, see plans in your ZIP code. A licensed insurance agent with Benefits Life can check which enrollment period applies to you at (602) SENIORS (602-736-4677), TTY 711, at no cost to you.
For Part A and Part B sign-up, contact Social Security at ssa.gov or 1-800-772-1213. For general Medicare questions, call 1-800-MEDICARE (1-800-633-4227, TTY 1-877-486-2048). See also When can I change my Medicare plan?
Sources
- Medicare.gov — When can I sign up for Medicare?
- Medicare.gov — Joining a health or drug plan
- Medicare.gov — Special Enrollment Periods
- eCFR — 42 CFR 422.62, election of coverage under an MA plan (including the emergency and major disaster SEP)
- eCFR — 42 CFR 423.38, Part D enrollment periods (monthly Extra Help and integrated D-SNP SEPs)
- eCFR — 42 CFR 422.74, disenrollment after more than 6 months out of the service area
- Medicare.gov — Avoid late enrollment penalties
- Medicare.gov — When can I buy Medigap?
Frequently asked questions
When is Medicare open enrollment for 2027 coverage?
The Annual Enrollment Period for 2027 coverage runs from October 15 to December 7, 2026. Changes you make take effect January 1, 2027. If you are in a Medicare Advantage plan, you get one more chance to change from January 1 to March 31, 2027.
I'm moving to Arizona from another state. When can I change my Medicare plan?
A permanent move gives you a special enrollment period. If your current Medicare Advantage or drug plan doesn't serve your new Arizona county, you can choose a new plan starting the month before you move (if you tell the plan in advance) and for 2 full months after you move. Original Medicare and Medigap move with you, but your Medigap premium may change.
Do I get a special enrollment period for a winter in Arizona?
Not just for traveling. A seasonal stay isn't a permanent move, so you keep your current plan. If you have a Medicare Advantage plan from another state and you're away from its service area for more than 6 months in a row, the plan must disenroll you, unless it has a visitor or traveler program; that disenrollment gives you a chance to choose new coverage.
What happens if I miss my Initial Enrollment Period for Part B?
If you don't have job-based coverage from current work, you can sign up during the General Enrollment Period, January 1 to March 31, and coverage starts the month after you sign up. You may owe a late enrollment penalty of 10% of the standard Part B premium for each full 12 months you could have had Part B but didn't, for as long as you have Part B.
I have AHCCCS. Can I change plans any time?
If you have AHCCCS and Medicare, or you get Extra Help, you can switch to a standalone Part D drug plan, or leave a Medicare Advantage drug plan for Original Medicare plus a drug plan, once a month. If you have full AHCCCS benefits, you can also join an integrated D-SNP once a month where one is available. The change starts the first day of the next month.
