Two enrollment windows fall between January 1 and March 31, after the fall Open Enrollment Period (October 15 – December 7). The Medicare Advantage Open Enrollment Period is for people already in a Medicare Advantage plan. The General Enrollment Period, on the same dates, is for people who missed signing up for Part A or Part B. This guide covers both for 2026 and 2027, with notes for Oregon.
The Medicare Advantage Open Enrollment Period
If you are enrolled in a Medicare Advantage plan on January 1, you can make one change between January 1 and March 31:
- Switch to a different Medicare Advantage plan, with or without drug coverage, or
- Drop your Medicare Advantage plan and return to Original Medicare. You can also join a standalone Part D drug plan at the same time.
If you are new to Medicare and joined a Medicare Advantage plan when you first got Medicare, you can make the same one change within your first 3 months of having Part A and Part B, even outside January through March.
The change takes effect the first day of the month after the plan gets your request.
| Request received in | New coverage starts |
|---|---|
| January | February 1 |
| February | March 1 |
| March | April 1 |
What you can and can't do
| Change | Allowed January 1 – March 31? |
|---|---|
| Switch from one Medicare Advantage plan to another | Yes, once |
| Drop Medicare Advantage for Original Medicare and add a Part D plan | Yes, once |
| Drop Medicare Advantage for Original Medicare without drug coverage | Yes, but you may owe a Part D late penalty later if you go without creditable drug coverage |
| Join Medicare Advantage from Original Medicare | No |
| Switch from one standalone Part D plan to another (Original Medicare) | No |
| Buy a Medigap policy without health questions | Only with a guaranteed-issue right (see below) |
Plan your Medigap before you leave Medicare Advantage. Oregon's Medigap rules (OAR 836-052-0142) give you a guaranteed right to buy a Medigap policy if, for example, you joined Medicare Advantage when you were first eligible at 65 or dropped a Medigap policy to join Medicare Advantage for the first time, and you leave within 12 months (the "trial right"), or if your plan ends or leaves your area. You generally have 63 days after the coverage ends to apply. Otherwise the company can ask health questions and may turn you down. Oregon's birthday rule doesn't help here: it is only for people who already have a Medigap policy. See Medigap in Oregon.
The General Enrollment Period (also January 1 – March 31)
If you didn't sign up for Part A (if you have to pay for it) or Part B when you were first eligible, and you don't qualify for a special enrollment period, you can sign up between January 1 and March 31. Coverage starts the month after you sign up. You may owe a late-enrollment penalty for as long as you have Part B: 10% of the standard premium for each full 12 months you could have had it.
If you delayed Part B because you or your spouse were still working and had job-based coverage, you probably have an 8-month special enrollment period instead. See the Part B special enrollment period and working past 65 in Oregon.
Special enrollment periods that work any time of year
Some situations give you a special enrollment period, whatever the month. Common ones:
- Your plan is ending. If your Medicare Advantage plan is not renewing for 2027, you have a special enrollment period through February 28, 2027. Choose a new plan by December 31, 2026 to avoid a gap. See plans ending in Oregon in 2027.
- You move out of your plan's service area, or to a new area with different plans.
- You lose job-based or union coverage.
- You get or lose Medicaid (OHP) or Extra Help. People with Extra Help or Medicaid can change standalone Part D plans, or leave Medicare Advantage for Original Medicare with a Part D plan, once a month.
- A declared emergency or major disaster, such as a wildfire, kept you from making a change you were eligible to make. See wildfire special enrollment in Oregon.
Oregon notes
- Not every county has plans to switch to. For 2026 and 2027, CMS data show no Medicare Advantage plan open to everyone in Grant, Harney, Lake, Umatilla or Union counties (only employer group plans), and Curry County has only a special needs plan. If you live there, your realistic choice is usually your employer plan or Original Medicare with a Part D plan. Check your county page.
- Elsewhere, choices vary by county. Statewide for 2027, CMS data show 61 Medicare Advantage plans open to everyone in their service areas, from 14 companies, and 8 standalone Part D plans.
- OHP members. OHA says that if you get Medicare while you have OHP, your CCO does not change, and OHP can help pay Medicare premiums, deductibles and coinsurance. Some Medicare Advantage plans, called D-SNPs, work closely with OHP. See OHP and Medicare.
- Bad weather and mail. In winter, rural and coastal mail can be slow. You can make changes online at Medicare.gov or by calling 1-800-MEDICARE (1-800-633-4227, TTY 1-877-486-2048), and keep the confirmation number.
How to switch plans between January and March
- Check what bothers you about your plan. Is it a doctor out of network, a drug not covered, or costs higher than expected? Your Annual Notice of Change and Evidence of Coverage show the details.
- Compare plans in your county. Check doctors, hospitals, pharmacies and your drugs. You can compare by ZIP code on PlanMatch or Medicare.gov, or you can request a call from a licensed insurance agent to review plans from the companies they work with.
- Enroll in the new plan. Joining a new Medicare Advantage plan ends your old one automatically. Don't cancel your old plan first, or you could have a gap.
- If you are going back to Original Medicare, join a standalone Part D plan (that also ends your Medicare Advantage plan), and apply for a Medigap policy if you want one, ideally before your Medicare Advantage coverage ends.
- Confirm and update. Save the confirmation number, watch for your new ID card, and give it to your doctors and pharmacy.
Sources
- Medicare.gov — Joining a plan (Medicare Advantage Open Enrollment Period and other enrollment periods)
- Medicare.gov — Special Enrollment Periods
- Medicare.gov — When does Medicare coverage start? (General Enrollment Period)
- 42 CFR § 422.62, Election of coverage under an MA plan (via Cornell LII)
- CMS — Dual/LIS and integrated care special enrollment periods job aid (January 1, 2025)
- Or. Admin. Code § 836-052-0142, Guaranteed issue for eligible persons (via Cornell LII)
- Oregon Health Authority — OHP and Medicare
- CMS — Medicare Advantage and Part D Landscape files, contract year 2027 (plan counts)
Frequently asked questions
What is the Medicare Advantage Open Enrollment Period?
It runs January 1 through March 31 each year. If you are enrolled in a Medicare Advantage plan, you can make one change: switch to another Medicare Advantage plan, with or without drug coverage, or drop your plan, return to Original Medicare and join a standalone Part D plan. People new to Medicare who joined a Medicare Advantage plan can also make one change within their first 3 months of Medicare.
Can I join Medicare Advantage from Original Medicare between January and March?
No. The Medicare Advantage Open Enrollment Period is only for people already in a Medicare Advantage plan. To move from Original Medicare to Medicare Advantage you generally need the fall Open Enrollment Period (October 15 to December 7) or a special enrollment period.
Can I get a Medigap policy if I leave Medicare Advantage during this period in Oregon?
Not automatically. Outside your Medigap open enrollment period, a Medigap company in Oregon can ask health questions unless you have a guaranteed-issue right, such as the 12-month trial right for people who joined Medicare Advantage for the first time, or your plan ending. Oregon's birthday rule applies only to people who already have a Medigap policy.
When does a change made in this period take effect?
The first day of the month after the plan gets your request. A request made in January starts February 1; in February, March 1; in March, April 1.
Medicare in your Oregon county
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