Medicare Annual Enrollment 2026: Dates, What You Can Change, and How Southern Californians Can Prepare

Every fall, Medicare gives beneficiaries one main opportunity to change their coverage for the coming year. If you're on Medicare in Los Angeles, San Diego, Orange County, Riverside, San Bernardino, Ventura, or Santa Barbara counties, this guide explains exactly what the Annual Enrollment Period is, what you can (and can't) do during it, and a simple month-by-month way to prepare — in plain English.

When is Medicare Annual Enrollment in 2026?

The Annual Enrollment Period (AEP) runs October 15 to December 7, 2026. Any change you make during this period becomes effective January 1, 2027.

If you make more than one change during AEP, the last change you make before December 7 is the one that counts.

What you can change during AEP

During October 15 – December 7 you can:

• Switch from Original Medicare to a Medicare Advantage plan (or the reverse)
• Switch from one Medicare Advantage plan to another
• Join, switch, or drop a stand-alone Part D prescription drug plan
• Return to Original Medicare and add a stand-alone Part D plan

What AEP is not for

• Enrolling in Medicare for the first time. If you're turning 65, that's your Initial Enrollment Period — see our Turning 65 in Southern California guide.
• Buying a Medicare Supplement (Medigap) policy. Medigap isn't tied to AEP. In California you can apply any time, though outside protected windows you may face medical underwriting. California's Birthday Rule gives Medigap policyholders 60 days from their birthday each year to switch to another Medigap plan with equal or lesser benefits, without underwriting.
• A second chance in the new year: if you're in a Medicare Advantage plan on January 1, the Medicare Advantage Open Enrollment Period (MA-OEP), January 1 – March 31, 2027, lets you make one switch to another Medicare Advantage plan or return to Original Medicare.

Why review your coverage even if you're happy with it

Plans change every year — premiums, deductibles, copays, drug formularies, provider networks, and extra benefits can all be different in 2027, and some plans leave the market entirely. In September, your Medicare Advantage or Part D plan will mail you an Annual Notice of Change (ANOC) describing exactly what's changing. Reading it is the single most useful 20 minutes of your Medicare year.

This matters in Southern California in particular: plan availability differs county by county — the Medicare Advantage options in Los Angeles County are not the same lineup as in San Diego or Riverside County. A plan that works well for a friend in another county may not even be offered where you live. (See our local pages for Los Angeles, San Diego County, and Riverside County.)

A simple month-by-month preparation timeline

July–August: take inventory

Make three lists: your doctors and specialists, your prescriptions (name, dosage, refill frequency), and what you actually spent on healthcare this year. If you've had any frustrations — a doctor leaving the network, a drug moving to a higher tier — write those down too. Our Medicare costs explained guide covers what the numbers mean.

September: read your ANOC

When your Annual Notice of Change arrives, check three things: your premium and deductible for 2027, whether your doctors are still in network, and whether your drugs are still on the formulary at the same tier.

October 1–14: research, but don't rush

Plan details for 2027 become available October 1. You can compare on Medicare.gov's Plan Finder or sit down with a licensed agent — but no changes can be submitted until October 15.

October 15 – December 7: make your change (if one makes sense)

Many people review their options and keep the plan they have. That's a fine outcome — the point is deciding, not switching.

December: confirm

If you changed plans, watch for your new plan's confirmation and ID cards before January 1, 2027.

Original Medicare + Medigap vs. Medicare Advantage: the fall decision

AEP is also when many Southern Californians reconsider their overall approach — bundled Medicare Advantage coverage versus Original Medicare paired with a Medigap policy and Part D plan. The trade-offs involve networks, out-of-pocket exposure, and monthly premiums, and the right answer depends on your health, budget, and travel habits. We compare them side by side in Medicare Advantage vs. Medicare Supplement.

One caution: if you leave Medicare Advantage for Original Medicare, a Medigap policy may require medical underwriting unless you qualify for a guaranteed-issue right. Talk this through before you drop anything.

Common AEP mistakes to avoid

• Ignoring the ANOC and getting surprised by January cost changes
• Choosing a plan only by premium without checking the drug formulary
• Assuming your doctor takes "Medicare Advantage" generally (networks are plan-specific)
• Missing the December 7 deadline and having to wait for MA-OEP or a Special Enrollment Period
• Dropping coverage before new coverage is confirmed

More in Common Medicare mistakes (and how to avoid them).

Frequently asked questions

What are the exact dates of the Medicare Annual Enrollment Period for 2026?

October 15 through December 7, 2026. Changes take effect January 1, 2027.

Can I switch from Medicare Advantage back to Original Medicare during AEP?

Yes. You can return to Original Medicare and add a stand-alone Part D plan. If you also want a Medigap policy, be aware that outside guaranteed-issue situations, insurers in California may apply medical underwriting.

Does AEP apply to Medigap plans?

No. Medigap enrollment isn't tied to AEP. California's Birthday Rule provides an annual 60-day window, starting on your birthday, to switch to a Medigap plan of equal or lesser benefits without underwriting.

What happens if I do nothing during AEP?

Your current plan generally renews automatically for 2027 with whatever changes were described in your ANOC — which is why reading the ANOC matters even if you plan no changes.

Where can I get free help in Southern California?

You can contact Medicare.gov or 1-800-MEDICARE, get free unbiased counseling from California's Health Insurance Counseling & Advocacy Program (HICAP) — California's State Health Insurance Assistance Program (SHIP) — at 1-800-434-0222, or work with an independent licensed insurance agent at no cost to you.

Sources & further reading

• Medicare.gov — enrollment periods & when you can join a plan
• CMS.gov — Centers for Medicare & Medicaid Services
• California HICAP — free, unbiased Medicare counseling (California's SHIP)
• California Department of Insurance

Last reviewed: July 2026. Medicare details can change annually — confirm current dates and amounts at Medicare.gov. Educational information only, not individualized advice.