Medicare Open Enrollment 2026: The 7 Mistakes That Cost Retirees Real Money
At a glance: Medicare Open Enrollment runs October 15 to December 7, 2026, and changes take effect January 1, 2027. Your plan was required to mail you an Annual Notice of Change (ANOC) — received by September 30 — with your 2027 premium, deductible, drug list and network. The expensive mistakes are rarely dramatic: an unopened letter, a premium compared instead of a total, a drug quietly dropped. One dropped drug can cost $6,240 a year at full price — and because it is no longer covered, not one dollar of it counts toward the 2027 out-of-pocket cap of $2,400. Below: the seven mistakes, in dollars, and the 20-minute check that avoids them.
Every fall, Medicare plans rewrite themselves. The name on your card stays the same; the premium, the drug list, the pharmacy terms and the doctor network underneath it can all change on January 1. Open Enrollment — October 15 through December 7 — is the one window when you can react. This desk sells no plans; it reads the season as we read everything here — one situation, answered in dollars, checked against Medicare's own documents.
What you can actually change before December 7
Between October 15 and December 7, Medicare's Open Enrollment page gives you this menu:
| If you have… | During Open Enrollment you can… |
|---|---|
| A Medicare Advantage plan | Join, drop, or switch to another Advantage plan — with or without drug coverage — or add/drop the drug coverage |
| Original Medicare | Switch to a Medicare Advantage plan |
| A Medicare Advantage plan | Switch back to Original Medicare (and join a separate drug plan) |
| Original Medicare + a drug plan | Join, drop, or switch to another Medicare drug plan |
Two mechanics matter. First, changes take effect January 1, 2027 — and your new plan must receive your request by December 7, so a form mailed that day is a gamble, not a plan. Second, you can change your mind inside the window: Medicare works from the last enrollment received by December 7. And Medicare attaches one caution to switching back: you may need a separate drug plan, and if you want a Medigap policy too, there are limits on when you can add one — Mistake 7 is the expensive version of that sentence.
Start with the letter: your Annual Notice of Change
If you are in a Medicare Advantage plan or a stand-alone drug plan, federal regulations (42 CFR 422.2267 and 423.2267) require your plan to get the Annual Notice of Change to you for receipt no later than September 30; its companion, the Evidence of Coverage, follows by October 15. The ANOC is not marketing — it is the one place your plan must tell you what your coverage becomes on January 1. Three things readers get wrong about it:
- It only comes from an Advantage or drug plan. Original Medicare by itself sends no ANOC — there is no plan to change. Medigap plus a drug plan? Your ANOC comes from the drug plan only.
- "No letter" is itself a finding. If yours never arrived, call the plan for another copy — never reconstruct next year's coverage from this year's card.
- The summary pages hide the money pages. The premium line sits up front because it is simple; the formulary and network changes — the ones worth thousands — sit deeper.
The 7 mistakes
Mistake 1: Doing nothing because "my plan was fine this year"
Doing nothing is a decision — it renews you into the 2027 version of your plan, whatever that version costs and covers. Plans are one-year contracts; last year's fit proves nothing about next year. The ANOC exists precisely because "the same plan" is a name, not a promise. (A discontinued plan says so in a separate non-renewal notice — do not confuse the two envelopes.)
Mistake 2: Shopping on the premium alone
The "premium" is the only number in the television ads, and the least informative number in the comparison. Your real "cost" of a drug plan is premium + deductible + what you pay for your actual drugs; an Advantage plan adds copays and the plan's medical out-of-pocket maximum. The 2027 frame, set by CMS in its CY 2027 Rate Announcement, shows how far premium and cost can separate:
| 2027 Part D standard figures (CMS) | 2026 | 2027 |
|---|---|---|
| Standard deductible (no plan may charge more) | $615 | $700 |
| Yearly out-of-pocket cap on covered drugs | $2,100 | $2,400 |
| Standard cost-sharing after the deductible | 25% | 25% |
One plan advertises a bargain premium and hands you the full $700 deductible; another charges more per month and pays from the first fill. CMS projects the average stand-alone drug-plan premium will barely move in 2027 — about $36 a month — which is exactly why averages are useless: your plan's own jump is in your ANOC.
Mistake 3: Assuming your prescriptions are still covered
This is the most expensive line in the letter. Every fall, plans move drugs between tiers, add prior-authorization rules, and drop drugs from the formulary outright. A tier move raises your copay. A drop is worse: a drug your plan does not cover is bought at full retail price — and because the $2,400 cap counts only covered Part D drugs, that spending never moves you one inch closer to the cap. The worked example below prices it: $6,240 a year on one ordinary brand-name drug. Check every drug you take — name, dose and form — against the 2027 list.
Mistake 4: Assuming your doctors are still in your plan
Advantage networks are renegotiated constantly: a hospital system or specialist group in-network in 2026 can be out in 2027 — announced, if anywhere, in the ANOC. Out-of-network care in an HMO generally means you pay the whole bill; in a PPO, a much larger share. Verify your specific doctors and your hospital for 2027 — with the doctor's office as well as the plan directory, because directories lag reality. If your doctor is leaving, that alone is a legitimate reason to switch — this fall, while switching is allowed.
Mistake 5: Forgetting the pharmacy is part of the price
The same drug, in the same plan, can cost more at a pharmacy that is merely "in network" than at one the plan calls "preferred" — and plans change which pharmacies are preferred. Compare plans at the pharmacy you will actually use, and check whether yours keeps its status in 2027. Skipping this check quietly taxes every fill, all year.
Mistake 6: Missing December 7
After December 7, the door mostly closes. One real second chance exists, for people already in an Advantage plan only: the Medicare Advantage Open Enrollment Period, January 1 to March 31 — switch to another Advantage plan, or leave Advantage for Original Medicare and join a separate drug plan. It does not let someone in Original Medicare join Advantage, nor let you swap one stand-alone drug plan for another. Beyond that, changes wait for a Special Enrollment Period — a move, lost coverage, Extra Help — or for next fall.
Mistake 7: Switching back to Original Medicare without checking the Medigap door
Leaving Advantage for Original Medicare is easy — a form before December 7. Replacing what Advantage bundled is the hard part. Original Medicare has no out-of-pocket maximum, which is why most switchers also want a Medigap policy — and outside your initial protected windows, Medigap insurers in most states can medically underwrite you: charge more, or decline you outright. Price the Medigap policy and confirm you can actually buy it before you drop the Advantage plan — in that order, not the reverse.
What one dropped drug costs: meet Carol
Carol is a made-up example: her plan's premium and copay figures are illustrative. Every program rule and 2027 figure around her is from Medicare and CMS documents, cited below.
Carol is 73, on Original Medicare with a stand-alone drug plan. She takes one brand-name maintenance drug whose full price is $520 a month. In 2026 her plan covered it on Tier 3 at a $95 copay and her premium was $18.40 a month — the drug cost her $95 × 12 = $1,140 last year. Her ANOC for 2027 said two things: the premium rises to $31.90 a month — the line most people read — and, deeper in the letter, the brand drug is not on the 2027 formulary at all. Her 2027, both ways:
| Carol's 2027 | Premiums (12 mo) | The brand drug (12 mo) | Total |
|---|---|---|---|
| Do nothing (stay) | $31.90 × 12 = $382.80 | $520 × 12 = $6,240 at full price | $6,622.80 |
| Switch (plan that covers it, Tier 3, $95) | $24.60 × 12 = $295.20 | $95 × 12 = $1,140 | $1,435.20 |
The difference is $5,187.60 in one year — from one drug, in one letter. The premium increase that makes the headline costs Carol $13.50 × 12 = $162 a year; the formulary line costs $6,240 — and because a non-covered drug is outside Part D, none of it counts toward the $2,400 cap. Had the drug stayed covered, her worst case would have been the cap itself: $2,400, then $0 for covered drugs for the rest of 2027. Coverage is the difference between a capped cost and an uncapped one.
Get the free one-page Open Enrollment Checklist: The 7 Checks Before Dec 7 — it decodes the ANOC's five money lines and walks Carol's seven checks, with the 2027 numbers printed on it. Get the free checklist (PDF) → or have it sent to your inbox →.
The 20-minute check that avoids all seven
You need your ANOC, your drug list, and Medicare's own comparison tool:
1. Lay out the paper. ANOC beside a list of every prescription — name, dose, how often — plus your doctors and your pharmacy.
2. Mark the ANOC's five money lines: new premium · deductible change · each drug's 2027 tier (or absence) · doctors' network status · pharmacy's status.
3. Open Medicare's Plan Finder (Medicare.gov/plan-compare) and enter your drugs and pharmacy exactly. Medicare's own guidance: add all your regular prescriptions — the estimate is only as honest as the list you give it.
4. Sort by total yearly cost, not premium — for your current plan's 2027 version and the alternatives.
5. In an Advantage plan, check the doctors for the finalists — then confirm with their offices.
6. Enroll before December 7 if switching; keep the confirmation; watch for the new plan card in December.
7. Stuck? Your State Health Insurance Assistance Program (SHIP) gives free local counseling, and 1-800-MEDICARE (1-800-633-4227) runs around the clock. Neither sells plans — which is why this desk points you there, not to an ad.
What plan shopping can't fix: your IRMAA surcharge
One number follows you from plan to plan, because no plan sets it: the income-related monthly adjustment amount (IRMAA). If your income two years ago crossed Medicare's lines, a surcharge is added to your Part B premium and to any drug plan's premium — switch plans and it comes with you. Our Medicare IRMAA Brackets 2026 guide lays out every tier. Two corollaries: income you create this year — a big Roth conversion, say — sets your IRMAA two years from now, a loop worked through in Does a Roth Conversion Raise Your Medicare Premiums?; and a surcharge that lands after your income fell — retirement is the classic case — can be appealed. See the FAQ below.
When staying put is the right answer
Honesty cuts both ways at this desk: sometimes the review ends with the plan you already have.
- Your ANOC is genuinely quiet — premium steady, every drug on the same tier, doctors and pharmacy unchanged. Then staying is not Mistake 1; the mistake is never having looked. You looked. Done.
- You are mid-treatment with a team your plan covers, and every alternative breaks that team. Continuity of care is a real cost too.
- You carry Extra Help or a Medicare Savings Program. Your windows work differently — you can change drug coverage more often than once a year — so check how a switch interacts with your help first.
The readers who lose money this season rarely chose the "wrong" plan from a compared shortlist. They never compared at all.
Frequently asked questions
When is Medicare Open Enrollment for 2027 coverage, and when do changes start?
October 15 through December 7, 2026. Changes take effect January 1, 2027, and your plan must receive your request by December 7 — enroll online or by phone, not by December mail.
What happens if I do nothing?
You are renewed into your current plan's 2027 version — new premium, new drug list, new network and all. "Nothing" is only safe after reading the ANOC and confirming the 2027 version still covers your drugs and doctors.
My Annual Notice of Change never arrived. What do I do?
Call your plan and request another copy — it was due to you by September 30. Meanwhile, Medicare's Plan Finder already shows 2027 details, so your comparison need not wait for the mailbox.
I missed December 7. Is there any second chance?
A narrow one. In a Medicare Advantage plan, January 1–March 31 gives you one change: another Advantage plan, or back to Original Medicare with a separate drug plan. With a stand-alone drug plan there is no equivalent window — changes wait for a Special Enrollment Period (a move, lost coverage, Extra Help) or next fall. And do not drop drug coverage meanwhile hoping to rejoin later: 63 days or more without Part D or other creditable coverage can add a late-enrollment penalty — 1% of the national base premium for every month uncovered — to every premium afterward, for as long as you have drug coverage.
Does the $2,400 cap mean my drug costs can't exceed $2,400 in 2027?
For covered Part D drugs, yes: once your out-of-pocket spending reaches $2,400, you pay $0 for covered drugs for the rest of 2027. Three honest limits: the cap counts what you pay for covered drugs — deductible, copays, coinsurance — not your premium; a drug your plan does not cover sits entirely outside it (Carol's $6,240); and the deductible itself can reach $700 in 2027, though many plans charge less or none.
My premium jumped because of an income surcharge (IRMAA). Will switching plans remove it?
No — IRMAA is calculated from your tax return, not your plan, and the same surcharge is added to whichever drug plan you choose. What can change it: time, or a successful appeal. If the income that triggered it has since dropped after a life-changing event — retirement is the classic case — ask Social Security to reassess using Form SSA-44; our SSA-44 appeal guide walks the process step by step.
Run the seven checks before December 7: the free Open Enrollment Checklist: The 7 Checks Before Dec 7 puts the ANOC's five money lines, the seven checks, and the official 2027 numbers on one printable page. Get the free checklist (PDF) → or have it emailed to you →.
Sources & official figures
- Medicare.gov — Open Enrollment (October 15–December 7; changes effective January 1; plan must receive your request by December 7; what can be joined, dropped or switched; the Medigap caution): https://www.medicare.gov/health-drug-plans/open-enrollment
- Medicare.gov — Joining a plan (Medicare Advantage Open Enrollment Period, January 1–March 31; Special Enrollment Periods; Plan Finder drug-entry guidance): https://www.medicare.gov/basics/get-started-with-medicare/get-more-coverage/joining-a-plan
- Centers for Medicare & Medicaid Services — Announcement of Calendar Year (CY) 2027 Medicare Advantage Capitation Rates and Part C and Part D Payment Policies (April 6, 2026), Table V-2: deductible $700 (2026: $615), out-of-pocket threshold $2,400 (2026: $2,100), 25% standard cost-sharing: https://www.cms.gov/files/document/2027-announcement.pdf
- Centers for Medicare & Medicaid Services — Medicare Advantage and Medicare Prescription Drug Programs Expected to Remain Stable in 2027 (source of the ~$36/month average stand-alone premium projection for 2027): https://www.cms.gov/newsroom/press-releases/medicare-advantage-medicare-prescription-drug-programs-expected-remain-stable-2027
- Code of Federal Regulations — 42 CFR 422.2267(e)(3) and 42 CFR 423.2267(e)(3) (Annual Notice of Change for enrollee receipt no later than September 30; Evidence of Coverage by October 15)
- Medicare.gov — What does Medicare cost? (Part D late-enrollment penalty: 1% of the national base premium per month without creditable coverage after 63 days, for as long as you have drug coverage): https://www.medicare.gov/basics/get-started-with-medicare/medicare-basics/what-does-medicare-cost
Last updated: October 25, 2026 — figures checked against Medicare.gov and CMS sources on October 24, 2026.
Disclaimer: The Retirement Desk publishes education, not insurance, financial, tax, or legal advice, and does not sell or endorse any Medicare plan. Carol is a hypothetical example with illustrative plan figures; your plan's 2027 terms are the ones printed in your own Annual Notice of Change. Plan availability and costs vary by ZIP code. Confirm your options at Medicare.gov/plan-compare, with your State Health Insurance Assistance Program (SHIP), or at 1-800-MEDICARE before enrolling.
Filed under: Medicare — The Retirement Desk, the situation-first retirement money desk for Americans 60–75.
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