Medicare Enrollment Periods and Deadlines Explained
Every Medicare enrollment window in one place: the Initial Enrollment Period, Annual Enrollment October 15 to December 7, Medicare Advantage Open Enrollment, Special Enrollment Periods, the Medigap window and New Jersey's rules for people under 65.
Medicare only lets you join or change coverage at set times. The big ones are your seven-month Initial Enrollment Period around your 65th birthday, the Annual Enrollment Period from October 15 to December 7 each year (changes start January 1), the Medicare Advantage Open Enrollment Period from January 1 to March 31, and Special Enrollment Periods triggered by events like retiring or moving. Medicare Supplements follow their own clock: a one-time six-month window that starts when you are 65 and enrolled in Part B. People under 65 on disability, people born on the first of a month and people who must buy Part A have their own rules, covered below. Right now, October 15 to December 7, 2026 is the window to choose coverage for 2027.
Every window at a glance
| Window | When | What you can do |
|---|---|---|
| Initial Enrollment Period | 3 months before your 65th birthday month, that month, and 3 months after | Sign up for Parts A and B; join a Medicare Advantage or Part D plan |
| Annual Enrollment Period | October 15 to December 7 each year | Join, switch or drop Medicare Advantage and Part D plans; changes start January 1 |
| Medicare Advantage Open Enrollment | January 1 to March 31 | If you are in a Medicare Advantage plan: switch to another one, or return to Original Medicare and add Part D (one change) |
| General Enrollment Period | January 1 to March 31 | Sign up for Part B (or Part A) if you missed your first window; coverage starts the month after you sign up |
| Special Enrollment Periods | Usually 2 to 8 months after a qualifying event | Enroll or change plans after events like losing employer coverage or moving |
| Medigap Open Enrollment | 6 months starting the month you are 65 and enrolled in Part B | Buy any Medicare Supplement sold in New Jersey without health questions |
Source: NJ Medicare Supplement coverage sold in New Jersey for those under age 50 (updated May 21, 2026).
Your Initial Enrollment Period
The Initial Enrollment Period is seven months long. If you turn 65 on May 5, it runs from February 1 through August 31. Sign up during the three months before your birthday month and Medicare starts on the first day of your birthday month. Sign up during your birthday month or the three months after, and coverage starts the first of the month after you sign up.
If your birthday is on the first of the month, Medicare treats you as turning 65 in the month before. Someone born June 1 has an Initial Enrollment Period of February 1 through August 31, and coverage can start May 1. Our Medicare enrollment date calculator on the Tools page works out your exact window from your birth date.
If you are already receiving Social Security, you are enrolled in Parts A and B automatically. You still need to choose a Medicare Advantage plan, or a Medicare Supplement and Part D plan, yourself.
Your first chance to join a Medicare Advantage plan, which Medicare calls the Initial Coverage Election Period, usually matches your Initial Enrollment Period. If you delay Part B because you are still working, it is the three months just before your Part B starts.
If you are under 65 and on disability
Your disability Initial Enrollment Period is the seven months around your 25th month of disability benefits, and you can join a Medicare Advantage or Part D plan then. When you turn 65 you get a fresh Initial Enrollment Period, and a fresh chance to choose plans. Who qualifies on disability, ALS or End-Stage Renal Disease is covered in our Medicare eligibility guide.
For Medigap, New Jersey's clock for this group is your first 12 months of Part B, when a company cannot turn you down for Plan D (NJ Division of Aging Services). At 65 a new six-month Medigap Open Enrollment Period opens for any plan.
If you have to buy Part A
If you have fewer than 40 quarters of work and must pay for Part A ($311 or $565 a month in 2026, CMS), the timing rule is simple: buy it in your Initial Enrollment Period, because a late Part A purchase carries its own surcharge. Our eligibility guide explains the quarters and the help available.
The Annual Enrollment Period, October 15 to December 7
This is the window everyone on Medicare shares. You can join a Medicare Advantage plan, switch from one to another, drop Medicare Advantage and return to Original Medicare, or join, switch or drop a Part D plan. Whatever you choose takes effect January 1.
Plans mail an Annual Notice of Change by September 30 listing what is different next year: premiums, copays, networks and drug lists. Plans renew automatically, so if you do nothing you keep the same plan with its new terms. That is why Jackie reviews every client's coverage each fall rather than assuming last year's plan still fits.
Medicare Advantage Open Enrollment, January 1 to March 31
If you are in a Medicare Advantage plan on January 1, you get one more change before March 31. You can switch to a different Medicare Advantage plan, or leave Medicare Advantage for Original Medicare and join a standalone Part D plan. You cannot use this window to move from Original Medicare into Medicare Advantage, and you get one change only. If you are new to Medicare and joined a Medicare Advantage plan, you also get a one-change window during your first three months of Medicare.
Special Enrollment Periods
Life events open their own windows. These are the ones Jackie sees most often:
- Losing employer or union coverage, from your own job or your spouse's: 8 months to sign up for Part B without a penalty, and 2 months to join a Medicare Advantage or Part D plan.
- Moving out of your plan's service area, or moving to New Jersey: a window to choose a plan that serves your new county.
- Moving into or out of a nursing home or other institution.
- Qualifying for, or losing, NJ FamilyCare (New Jersey Medicaid) or Extra Help.
- Your plan leaving Medicare or your area, or Medicare ending its contract with the plan.
- Joining a plan with a 5-star overall rating, once a year.
The fall and winter calendar, 2026 to 2027
If you already have Medicare, these are the dates that matter this season, in order:
- By September 30, 2026: your plan's Annual Notice of Change arrives. Read it before October 15.
- October 15, 2026: Annual Enrollment opens for 2027 Medicare Advantage and Part D plans.
- December 7, 2026: the last day to make an Annual Enrollment change. A choice made on December 8 is too late unless another window applies.
- January 1, 2027: your 2027 plan, new or renewed, takes effect, along with its new premium, copays and drug list.
- January 1 to March 31, 2027: Medicare Advantage members get one more switch. The General Enrollment Period for a missed Part B signup runs on the same dates.
- April 1, 2027 onward: outside a Special Enrollment Period, your coverage is set until next October.
The General Enrollment Period
If you missed your Initial Enrollment Period and do not qualify for a Special Enrollment Period, you can sign up for Part B between January 1 and March 31. Coverage starts the first of the month after you sign up, and a lifelong late surcharge may apply. Our late enrollment penalties guide works out what it costs.
The Medigap window, and why it matters most here
Your Medigap Open Enrollment Period is six months long and starts the first month you are both 65 and enrolled in Part B. During it you can buy any Medicare Supplement sold in New Jersey, at the same price as a healthy person. It happens once and does not repeat.
New Jersey has no birthday rule or yearly window to switch Medigap policies without health questions (NAIC chart as of May 11, 2026). The federal guaranteed issue rights still apply, for example when your Medicare Advantage plan leaves your area or you move out of its service area, and so do the federal trial rights: if you joined a Medicare Advantage plan when first eligible at 65, you can switch to a supplement without health questions within your first year.
Which deadline applies to you?
- Turning 65 and not working: your Initial Enrollment Period, then your Medigap window.
- Working past 65 with group coverage from current work: a Special Enrollment Period when the job or coverage ends, and your Medigap window starts with Part B.
- Already on Medicare and unhappy with your plan: October 15 to December 7, or January 1 to March 31 if you are in Medicare Advantage.
- Moving, losing NJ FamilyCare or qualifying for Extra Help: a Special Enrollment Period tied to that event.
- Under 65 on disability: your first 12 months of Part B for New Jersey's Plan D, then a new Medigap window at 65.
- Missed everything: the General Enrollment Period, January 1 to March 31.
The bottom line
Most people only need three dates: their Initial Enrollment Period, the October 15 to December 7 Annual Enrollment Period every year, and their one-time Medigap window. For 2027 coverage, the window is open now through December 7, 2026. If you are retiring, on disability, born on the first of the month or buying Part A, the dates shift, so check them early. If a life event has you wondering which window applies, call or text Jackie at (856) 727-4221 before a deadline passes.
Want to go through this with someone?
Jackie Layser will go through your doctors, your prescriptions and your real numbers by phone, Zoom or in person, and explain plainly what we found. Solutions You Can Count On.
Prefer to talk it through? Book a no-cost consultation by phone, Zoom or in person, and find official Medicare forms and publications on our Resources page.
Sources
- When can I sign up for Medicare?, Medicare.gov (CMS)
- Avoid late enrollment penalties, Medicare.gov (CMS)
- 2026 Medicare Parts A and B premiums and deductibles, Centers for Medicare & Medicaid Services
- State Medigap rules: birthday rule and coverage under 65 (as of May 11, 2026), National Association of Insurance Commissioners
- NJ Medicare Supplement coverage for people between ages 50 and 65 on Medicare due to disability (September 2026), NJ Division of Aging Services
- NJ Medicare Supplement coverage sold in New Jersey for those under age 50 (updated May 21, 2026), NJ Division of Aging Services
- Medicare Savings Programs, Medicare.gov (CMS)
Please note: We do not offer every plan available in your area. Any information we provide is limited to those plans we do offer in your area. Please contact Medicare.gov or 1-800-MEDICARE to get information on all of your options. Garden State Medicare Solutions is not connected with or endorsed by the United States government or the federal Medicare program. Medicare has neither endorsed nor reviewed this information.