When does Medicare open enrollment start in Arizona for 2027?
The window itself is the easy part: October 15 to December 7, same as every year. The part people miss is what lands in the mailbox before it opens, and the fact that in north Peoria the thing most likely to have changed is not the premium — it is which Arrowhead and Sun City practices the network still reaches.
October 15 through December 7 — the same dates as every year, with whatever you change taking effect January 1, 2027. There is no separate Arizona window and nothing opens early in Maricopa County. If you live in Peoria and someone tells you enrollment is “already open” in August, they are selling you something.
The dates are not the useful part, though. The useful part is what shows up in your mailbox six weeks before the window opens, and what you do with it in the two hours after you open it.
When does Medicare open enrollment start for 2027?
October 15, 2026. It closes December 7, 2026, and the coverage you pick starts January 1, 2027.
Inside that window you can join, drop or switch a Medicare Advantage plan; join, drop or switch a standalone Part D drug plan; and move between Original Medicare and Medicare Advantage in either direction. Whatever you choose replaces what you have on January 1 — you do not need to cancel the old plan, and you should not try to.
December 7 is a real deadline. The plan finder does not stay open a few extra days, and “I meant to look at it” is not a Special Enrollment Period.
The letter that arrives before the window opens
If you are on a Medicare Advantage or Part D plan, your insurer must send you an Annual Notice of Change — the ANOC — no later than September 30. It is a fat envelope, it looks like the marketing mail that starts piling up around the same time, and it is the only document that tells you what your own plan is doing on January 1.
Four things to find in it, in this order:
- The drug formulary changes. A medication moving from tier 2 to tier 3, or off the list entirely, is the change that costs the most and is buried the deepest.
- The provider network changes. Plans add and drop practices and hospital systems every year. This is the one that matters most in Peoria — more on that below.
- Premium, deductible and the maximum out-of-pocket. Read the out-of-pocket maximum, not just the premium. A plan that keeps a $0 premium and raises its ceiling by a few thousand dollars did not stay the same.
- Whether the plan is being offered at all next year. A non-renewal comes as its own separate notice, and it is the one situation where doing nothing genuinely hurts you.
If your ANOC has not arrived by the first week of October, call the plan. Original Medicare does not send one — Parts A and B are set by federal law, not by an insurer, so there is nothing plan-specific to notify you about.
In north Peoria, the network is what changed
Here is the local version, and it is the reason a national checklist only gets you halfway.
Peoria runs close to thirty miles north to south. Up in the 85383 corridor — Vistancia, Trilogy, Blackstone, the newer stretch either side of Lake Pleasant Parkway — most households drive to Arrowhead or into Sun City for specialist care. Primary care is close by; the cardiologist, the orthopedist and the oncologist usually are not. That means the plan’s usable footprint from your driveway is decided almost entirely by whether those specific practices are still in-network on January 1.
Down in the 85345 core and around Westbrook Village, the pattern flips: a denser cluster of nearby options, and a lot of households who have used the same physician for twenty years and are not interested in a plan that makes them stop.
Two neighbors on the same street can renew the identical plan and have completely different years, because one of them lost a specialist in the network appendix nobody reads. So when the ANOC lands:
- Check your doctors by name, not by hospital system. A system can be in-network while the individual practice you were referred to is not, and the reverse happens too.
- Check the specialists you drive for, not only the primary care office five minutes away.
- Check the pharmacy tier. Preferred-versus-standard pharmacy status moves around, and in a market this size there is usually a preferred option within a few miles.
How Medicare Advantage networks are actually drawn explains the mechanics, and the Peoria service-area page has the local picture. If your ZIP sits on the Peoria–Glendale seam, the Glendale page is the one to read.
What open enrollment does not let you do
This is where the fall gets misunderstood, so it is worth a table.
| Window | Dates | What it lets you do |
|---|---|---|
| Annual open enrollment | Oct 15 – Dec 7, 2026 | Join, drop or switch Medicare Advantage and Part D; move between Original Medicare and Advantage. Effective January 1. |
| Medicare Advantage open enrollment | Jan 1 – Mar 31, 2027 | Only if you are in an Advantage plan on January 1. One change: a different Advantage plan, or back to Original Medicare with a Part D plan. |
| Medigap open enrollment | The six months from when your Part B starts | Buy any Medicare Supplement sold in Arizona with no health questions. It is one-time and it is not in the fall. |
| Special Enrollment Period | Triggered by an event | A permanent move, losing employer coverage, a plan leaving your area. Available any time of year, on its own clock. |
| Initial enrollment at 65 | Your seven-month birthday window | Sign up for Parts A and B and choose your first coverage. Unrelated to the fall dates. |
Sources: Medicare.gov open enrollment and joining-a-plan pages; CMS open enrollment partner resources.
The one people most often get wrong: the fall window does not give you a Medicare Supplement. You can leave an Advantage plan in October and still be declined by the supplement carrier in November, and Arizona has no birthday rule to rescue you. If that is the move you are considering, the supplement gets approved first — I wrote out how that sequence works here. The enrollment timeline tool will show you which window you are actually in.
The 2026 numbers, and the ones that are not out yet
$202.90 a month — the standard Part B premium for 2026, unchanged by anything you do in the fall
The 2026 Part B deductible is $283, the Part A inpatient hospital deductible is $1,736 per benefit period, and Part D has a hard annual out-of-pocket cap of $2,100 on covered drugs. Switching plans in October does not move any of these — they are set nationally. What does move your Part B premium is income: IRMAA begins above $109,000 for a single filer and $218,000 filing jointly, based on your 2024 tax return.
Source: CMS 2026 Parts A & B premiums and deductibles, and the CMS Part D 2026 figures. Verified against cms.gov.
The 2027 versions of those figures are published by CMS in the fall, usually in November — partway through the enrollment window rather than before it. That is not a reason to wait. Your plan’s own 2027 costs are in the ANOC by September 30, and the federal numbers move by a few dollars, not by enough to change which plan fits.
If a one-off event pushed your income up two years ago — a home sale, a Roth conversion, the year you actually retired — check where you land and talk to your tax advisor about appealing on Form SSA-44. That is a separate track from anything you do in October.
A working plan, from now to December 7
You have about eight weeks before the mail starts. Use them like this:
- Now: write down your prescriptions with dosages, your pharmacy, and the doctors you would not want to give up — including the Arrowhead and Sun City specialists. Every honest comparison starts here and none can be done without it.
- By September 30: find the ANOC when it arrives and do not throw it out. Put it with the list from step one.
- First week of October: read the four items above. If nothing you use changed, you are probably done.
- October 15 onward: if something did change, run your own list through the Medicare plan finder with your own ZIP, or have someone do it with you. Not your neighbor’s ZIP and not last year’s drug list.
- Before Thanksgiving: decide. The first week of December is the busiest week of the year for everyone in this business, and a rushed decision on December 6 is how people end up in a plan their cardiologist does not take.
If you would rather not do this alone, that is what I am here for. I will check your specific drug list and your specific doctors against what is actually offered in your ZIP for 2027, and if the answer is “stay where you are”, that is what you will hear — it is the answer for most people most years. The office is in Anthem, about 25 minutes from north Peoria out the Carefree Highway and down Lake Pleasant Parkway, and plenty of clients would rather do the whole thing over the phone. Call (602) 844-6002 or book a time. It costs nothing either way.
Common questions
When does Medicare open enrollment start for 2027?
Medicare's annual open enrollment period runs October 15 through December 7, 2026, and anything you change in that window takes effect January 1, 2027. The dates are the same every year and they are national — there is no separate Arizona window, and no early start for Maricopa County. December 7 is a hard deadline, not a soft one.
What is the Medicare Annual Notice of Change letter?
It is the notice your Medicare Advantage or Part D plan is required to send you each fall, by mail or electronically, no later than September 30, spelling out what changes about that plan on January 1 — premiums, deductibles, copays, the drug formulary and the provider network. Original Medicare does not send one, because Parts A and B are set by federal law rather than by a plan. It is thick, it looks like junk mail, and it is the single most useful document you will get all year.
What happens if I do nothing during Medicare open enrollment?
In most cases you are simply renewed into the same plan for the next year, with whatever changes the Annual Notice of Change described. That is a real choice and often the right one. The exception is a plan that is leaving your area or shutting down for the year — then you get a separate non-renewal notice, and if you ignore it you can end up back on Original Medicare with no drug coverage and a late-enrollment penalty building.
Do I have to re-enroll in Medicare every year?
No. Parts A and B continue automatically, and Medicare Advantage, Part D and Medicare Supplement plans generally renew on their own too. Open enrollment is your annual chance to change something, not a requirement to re-apply. What is worth doing every year is checking, because your prescriptions and your plan's terms both move.
Can I change my Medicare plan after December 7?
Sometimes. If you are enrolled in a Medicare Advantage plan on January 1, the Medicare Advantage open enrollment period from January 1 to March 31 lets you make one change — switch to a different Advantage plan, or drop back to Original Medicare and pick up a Part D plan. It does not apply if you are on Original Medicare, and it is not a second bite at the whole menu. Separately, life events such as a permanent move can trigger a Special Enrollment Period at any time of year.
Can I switch from Medicare Advantage to a Medigap plan during open enrollment?
You can leave the Advantage plan in that window, but the Medigap side is a separate application to an insurance company, and outside your one-time Medigap open enrollment Arizona generally allows medical underwriting. Arizona has no birthday rule, so approval is not guaranteed. Line the supplement approval up before you drop the Advantage plan, never the other way around.