Sometime between now and September 30, Medicare Advantage members across the country will pull an envelope out of the mailbox and learn what their coverage may look like in 2027. Most will receive an Annual Notice of Change. Members whose plan is leaving Medicare or exiting their county may receive a separate nonrenewal notice.. Others will trim benefits, tighten networks, or move drugs into higher tiers. The document is called the Annual Notice of Change, and the largest insurers have already told Wall Street what pressures will shape those letters.
On its July 16, 2026 earnings call, UnitedHealth Group (NYSE: UNH) said it expects full-year Medicare Advantage enrollment to shrink by approximately 1.1 million. UnitedHealthcare CEO Tim Noel told analysts the company will support margins through “benefit adjustments and selective changes in market participation” in its 2027 bids. That is the corporate way of saying some combination of leaner benefits and fewer markets.
Pharmacy retailer CVS Health (NYSE: CVS) offers another clue, though not a direct roadmap for Aetna’s 2027 Medicare plans. The company exited the individual ACA exchange business in 2026, reported lower medical membership, and is closing 16 Oak Street Health clinics. Humana (NYSE: HUM) is moving the other way, guiding to roughly 25% year-over-year growth in individual MA membership for 2026.
As of July 27, UnitedHealth shares were up about 26.5% year to date, Humana had gained roughly 48%, and CVS was ahead about 35%. Wall Street has rewarded retrenchment and growth alike, as long as the margins improve. Members are the ones who have to live with the fine print.
None of that matters to you until the letter arrives.
What the Fall Letter Actually Triggers
If your plan is continuing, it must deliver the Annual Notice of Change by September 30. Read the summary of changes first. If the plan is being discontinued, watch for a separate nonrenewal notice. Depending on what you receive, two enrollment windows may matter.
The first is the Annual Enrollment Period, October 15 through December 7. Anyone can switch MA plans, leave MA for Original Medicare, or change drug coverage during this window, with new coverage effective January 1, 2027.
The second applies when a plan does not renew. CMS grants affected members a Special Enrollment Period running from December 8 through the end of February. That window lets you choose another MA plan or drug plan after the ordinary enrollment deadline.
Separately, returning to Original Medicare because the plan is leaving Medicare or your area can open a federal guaranteed-issue right to Medigap. That application window can begin when the termination notice arrives and ends 63 days after the MA coverage ends. That distinction is the one most people miss.
The Medigap Trap Hiding in the Switch Back
Federal guaranteed-issue rights after an MA non-renewal are narrow. They generally cover Medigap Plans A, B, C, D, F, and G. Plans C and F are unavailable to people newly eligible for Medicare on or after January 1, 2020, who may buy Plan D or G instead. Plan N is not included under the federal rule unless state law provides wider protection.
Miss the window, and outside states with broader rights, including New York, Connecticut, Massachusetts, and Maine, an insurer may medically underwrite you, charge more, or deny coverage based on your health. A 72-year-old with diabetes and a stent who assumes she can “just go back to Original Medicare next year” could find the supplement door closed.
Original Medicare will carry its own costs in 2027. The Medicare Trustees project a standard Part B premium of $209.50 per month, up from $202.90 in 2026, and a $292 annual deductible, up from $283. Those are estimates; CMS will finalize the amounts this fall. The 2027 IRMAA calculation will use 2025 income, but the official thresholds and surcharges have not yet been released.
Using a Plan G premium of $150 to $250, Original Medicare plus Medigap could run roughly $360 to $460 a month before standalone drug coverage, and more for someone paying IRMAA. That math can push people toward another MA plan even when they dislike the network they are leaving.
What to Do When the Letter Lands
Three checks deserve your attention before the envelope disappears into a kitchen drawer.
- Read the ANOC and compare four items: whether the plan will still operate in your county, the premium and maximum out-of-pocket amount, the benefits you actually use, and your prescription tiers. Confirm doctors and hospitals separately with their billing offices because directories can lag.
- If the plan is non-renewing and you have a chronic condition, price Medigap while the guaranteed-issue right is open. Apply before the MA coverage ends if possible, and no later than 63 days afterward. Keep the termination notice as proof of eligibility.
- Run your current MA-PD plan or standalone Part D plan through Medicare.gov’s Plan Finder. Enter every prescription and pharmacy. Formularies move even when premiums do not, and auto-renewal is where most drug-cost surprises begin.
The insurers have already made their 2027 decisions. Yours starts when the letter arrives.
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