Two enrollment windows collide this fall, and both come with hard deadlines and 2026 rule changes that make coasting on your current plan a risky move. Medicare's Annual Enrollment Period runs October 15 to December 7, 2026, and the ACA Marketplace opens November 1 — so anyone shopping either type of coverage has roughly a one-month stretch to review options before Medicare closes on December 7 (MedicareAdvantage.com).
The stakes are higher this year because policy shifted underneath both programs. Medicare Part D prescription coverage gains a $2,100 annual out-of-pocket cap in 2026, yet the number of standalone prescription drug plans actually shrank by 22% from 2025 (KFF). On the Marketplace side, the enhanced tax credits that have capped premiums for millions expired at the end of 2025, pushing what many families pay sharply higher (KFF).
When is the 2026 Medicare Open Enrollment window?
Medicare's Annual Enrollment Period (AEP) — the window to enroll in or switch Medicare Advantage and Part D drug plans — runs October 15 through December 7, 2026, and any changes you make take effect on January 1, 2027 (MedicareAdvantage.com). That is the entire season. There is no extension and no second chance to shop again until the same window returns next October.
The window matters because almost no one is locked into the plan they have. During the AEP you can enroll in a Medicare Advantage plan (Part C), switch to a different one, or drop it and return to Original Medicare, and you can add, change, or drop a standalone Part D prescription plan. If you do nothing, you keep your current coverage — but you also keep whatever 2027 rate, cost-sharing, or formulary changes your plan is making. That is the quiet risk: staying put is still a choice with consequences.
What changed in Medicare Part D for 2026?
The biggest shift is cost protection. Under the Inflation Reduction Act, Part D has an annual out-of-pocket cap of $2,100 in 2026, up slightly from $2,000 in 2025: once your spending on covered medications hits that amount, you pay nothing for the rest of the calendar year (KFF). That cap applies only to covered Part D drugs — your monthly plan premium does not count toward it, and drugs covered under Part B (like many infused or injected treatments given in a doctor's office) are not protected by it (IBX).
The tradeoff is that choice is shrinking. In 2026, a total of 360 standalone Part D plans (PDPs) are offered across 34 regions — a 22% decrease from 2025 — and the number of parent organizations running them fell by 2 (KFF). Fewer plans means your current plan may not exist next year, its premium may climb more than usual, or its formulary — the list of covered drugs — may drop a medication you rely on. A plan that looked right in 2025 can be a poor fit in 2026 without any action from you.
What changed on the ACA Marketplace?
The Marketplace has its own separate calendar. Open enrollment for individual coverage runs November 1 through January 15 on HealthCare.gov, with a crucial double deadline: enroll by December 15 and your coverage begins January 1, but sign up between December 16 and January 15 and your start date is February 1 — and if your income qualifies you for the wrong plan in the meantime, you could be on the hook for a month of coverage you did not choose (Washtenaw Health Project).
The backdrop for 2027 shopping is a cost squeeze that began in 2026. The enhanced premium tax credits Congress introduced in 2021 and extended through 2025 expired at the end of that year, and Congress did not renew them for 2026 (KFF). Those credits had capped premiums as a share of income — an individual earning $28,000 paid roughly 1% of that income, about $325 a year, toward a benchmark plan; without the credits, the same person would face near 6%, or about $1,562 annually (KFF). In short, some households still qualify for a smaller credit while others lost their subsidy entirely and now pay meaningfully more.
Why skipping the annual review is the real risk
Both programs punish inaction differently, but the outcome is the same: you pay more or lose coverage you want. On the Marketplace, if you do not log in and actively choose a plan for next year, HealthCare.gov may auto-enroll you in something "similar," and the new coverage and costs may not fit your needs or your budget (Washtenaw Health Project). On Medicare, an unchanged plan quietly absorbs whatever premium increase and formulary changes your carrier made for the new year.
The single best habit this fall is to re-shop rather than renew on autopilot. Ask three questions of every plan before the deadlines: Are my doctors and pharmacy still in network? Are my specific medications still on the formulary, and at what tier? What is my real maximum out-of-pocket for the year? One caution on premiums: the Part D $2,100 cap does not count your monthly premium toward that limit (IBX), so a low-premium plan is not automatically the cheapest once you add drug costs.
Why a local agent earns its weight this season
Your deadline action plan
The decision tree is short once the dates are on a calendar. Put October 15 on it for Medicare AEP and shop Advantage and Part D plans before December 7 closes the window — changes go into effect in January (MedicareAdvantage.com). Put November 1 on it for the Marketplace, then aim to enroll by December 15 so coverage starts January 1 rather than February 1, and finish by January 15 at the latest (Washtenaw Health Project). Doing your homework this month — rather than the last day of each window — matters because carriers and HealthCare.gov all slow down near the deadlines.
Meet the deadlines early rather than on the last day. Agents, carrier portals, and HealthCare.gov all slow down as the closing dates approach, and a plan that is a fit is worth more than a plan that is merely available. Take one afternoon before Halloween to run your doctor list, prescriptions, and budget through your current plan, and you will find the biggest financial decision this fall is already half solved.
1What happens if I miss the December 7 Medicare deadline?
If you do nothing before December 7, 2026, your current Medicare Advantage or Part D plan simply continues into the new year — but so do whatever premium increases, formulary changes, or plan discontinuations your carrier made. You miss your one chance to switch until the same AEP window returns next October, and the Marketplace's separate deadline does not help: Medicare and Marketplace coverage are entirely different programs with separate sign-ups ([MedicareAdvantage.com](https://www.medicareadvantage.com/medicare-enrollment)).
2Does the Part D cap cover brand-name and specialty drugs?
Yes — the $2,100 cap applies to the cost of your covered Part D drugs, including brand-name and specialty medications, once you are enrolled in a Part D plan. What it does not count toward the limit is your monthly plan premium and drugs covered under Medicare Part B, such as many infused or office-administered treatments ([IBX](https://www.ibx.com/medicare/resources/for-members/inflation-reduction-act.html)). Check your specific plan's formulary during the AEP to see which of your medications are covered.
3Can I use the Marketplace if I miss Medicare enrollment?
No — the two programs are not interchangeable. The ACA Marketplace is for people under 65 who are not on Medicare and do not have employer coverage, while Medicare serves people 65 and older and certain younger people with disabilities. If you qualify for one, you generally do not use the other, so a missed Medicare deadline cannot be cured by signing up on HealthCare.gov instead ([MedicareAdvantage.com](https://www.medicareadvantage.com/medicare-enrollment)).
The Integrity Agency — Dover, NH
Licensed agent Ronald Plocinski compares Medicare Advantage and Part D plans with your own doctors and medications in mind.
Get a free plan reviewIf you would rather not sort through this alone, I'm here for that. The Integrity Agency in Dover, NH, reviews your doctors, prescriptions, and plan options before any deadline — a free, no-pressure second set of eyes on what is the biggest shopping window you will face all year. Book a call now and go into October 15 knowing which plans actually serve you.
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