Medicare Supplement in Washington State: How Medigap Works and the Rules That Make WA Different

In Washington, if you already have a Medigap policy, you can replace it with another one at any time of year without answering health questions. That comes from RCW 48.66.045: someone with a standardized Plan B through N can move to another B through N policy, and someone with Plan A can move to another Plan A, with no "evidence of insurability." Federal rules give no such right: outside your first six months or a guaranteed-issue situation, a Medigap company can use medical underwriting and can turn you down.

That one rule changes how Medicare Supplement Insurance works here. There's no annual window attached to it. It applies all year, as long as you're replacing Medigap with Medigap.

Below is how Medigap works in Washington state: what it pays, what it never pays, the lettered benefit designs, the Washington rules that go further than federal law, and the timing that still matters even with the switching right.

What Medigap is, and what it isn't

Medicare.gov's definition is plain enough: Medigap is extra insurance from a private company that helps pay your share of costs in Original Medicare, like deductibles, coinsurance and copayments. Medicare pays its share of the approved amount first. Then the Medigap policy pays its share.

To buy one you generally need both Part A and Part B. You pay the company a monthly premium on top of the Part B premium you already pay Medicare. Each policy covers one person, so a married couple buys two policies.

Now the limits, because this is where people get surprised:

• It doesn't work with Medicare Advantage. You can have Medigap or a Medicare Advantage plan, not both. Medigap can't pay Medicare Advantage copays, deductibles or premiums (Medicare.gov). If you join Medicare Advantage, you have a legal right to keep the Medigap policy, but it stops supplementing anything (CMS Medigap guide).
• No drug coverage. Medigap policies sold after 2005 don't include prescription drugs. For that you'd add a separate Part D plan.
• Not long-term care. CMS lists what Medigap generally doesn't cover: long-term care such as non-skilled care in a nursing home, vision, dental, hearing aids, glasses and private-duty nursing.

Once you have a policy, it's hard to lose. RCW 48.66.090 makes every Medicare supplement policy guaranteed renewable: the company can cancel only for nonpayment of premium or material misrepresentation.

The 2026 costs Medigap is built around

Medigap fills the gaps Original Medicare leaves you to pay. These are the government-set amounts for 2026. CMS usually announces the 2027 figures in November; I covered what to expect in the 2027 Part B premium post.

Source: CMS, 2026 Medicare Parts A & B premiums and deductibles fact sheet (Nov. 14, 2025); Medicare.gov, Medicare costs.

The Part B coinsurance is the one to watch. It's usually 20% of the Medicare-approved amount for doctors' and other providers' services after the deductible, so on a large outpatient bill your share grows with the bill.

Then there's the excess charge. A doctor who doesn't accept Medicare assignment can bill more than the Medicare-approved amount. Medicare.gov says that in many cases the charge can't be more than 15% above the approved amount (the "limiting charge"). I couldn't find a Washington law that bans or tightens excess charges, so plan as if the federal rule is what applies. Only Plans F and G pay excess charges.

If your income is limited, look at the Medicare Savings Programs before anything else. Details on Washington's 2026 income limits are in my Medicare Savings Program in Washington post.

The lettered plans: same benefits everywhere

Medigap policies are standardized. In Washington, as in most states, they're named by letter: A, B, C, D, F, G, K, L, M and N. Every policy with the same letter has the same basic benefits no matter which company sells it. CMS puts it bluntly: price is the only difference between policies with the same letter.

Source: CMS, Choosing a Medigap Policy, 2026 (Product No. 02110) benefit chart; K and L limits from Medicare.gov, compare Medigap plan benefits. *Plan N: copays of up to $20 for some office visits and up to $50 for emergency room visits that don't lead to an inpatient admission.

A few rows need a sentence each:

• C and F are closed to anyone new to Medicare since 2020. Policies sold to people new to Medicare on or after January 1, 2020 can't cover the Part B deductible, so C, F and high-deductible F aren't sold to them. You count as new if you turned 65 on or after that date and got Part A on or after it. People eligible earlier may still buy C or F. Washington wrote the same cutoff into its own rules (WAC 284-66-068).
• K and L have an out-of-pocket limit. In 2026 it's $8,000 for K and $4,000 for L. After you reach it and the yearly Part B deductible ($283), the policy pays 100% of covered services for the rest of the calendar year.
• High-deductible F and G. You pay up to $2,950 in 2026 in Medicare-covered costs before the policy pays anything. Under Washington's rules, high-deductible F is only for people eligible before 2020; high-deductible G may be offered to people eligible before or after 2020, where a company sells it.
• Foreign travel emergency. Where a letter includes it, the benefit is 80% of billed charges for emergency care that begins in the first 60 days of a trip outside the U.S., after a $250 calendar-year deductible, up to a $50,000 lifetime maximum (WAC 284-66-064).
• E, H, I and J are no longer sold. If you already have one, you can generally keep it.

Two more things CMS points out. Companies don't have to sell every letter; each decides which ones it offers, though all must offer Plan A. And some sell Medicare SELECT versions that require network hospitals (and sometimes doctors) for full benefits. The OIC handbook adds that you generally can't use a SELECT policy in other states, which matters if you winter in Arizona.

The table tells you what a letter pays. It doesn't tell you which letter fits you, and that depends on your health, your doctors, your budget and how much risk you can carry. That's a conversation, not a chart.

Washington rules vs. the federal minimum

Federal law sets the floor. Washington builds on it in the places that matter most to buyers:

Source: CMS, Choosing a Medigap Policy, 2026; Revised Code of Washington ch. 48.66 and WAC 284-66 as cited (app.leg.wa.gov), accessed Oct. 15, 2026.

How the year-round switching right works

The OIC's own summary: if you're already enrolled in a Medigap plan B through N, you can switch at any time to another plan B through N, and if you have plan A you can switch to another plan A, without a written health screening. The statute also covers replacing "other more comprehensive coverage," and it applies whether you got Medicare by age, disability or end-stage renal disease.

The right has edges. Know them before you rely on it:

• You can only move to letters the new company actually sells. The law requires a company to issue its standardized B through N plans; it doesn't force a company to sell every letter.
• C and F stay closed to anyone who became eligible on or after January 1, 2020, even when switching. For those people the list in RCW 48.66.045(2)(b) is B, D, G, high-deductible G, K, L, M and N.
• Coming from Medicare Advantage or another kind of plan is different. The OIC says that when you switch from some other type of health plan to Medigap, rules can vary and insurers may require a written health screening. A federal guaranteed-issue right may still apply (more on that below). If you're unsure, the OIC says to call its consumer hotline at 800-562-6900 and ask for a health compliance analyst.

Pre-existing conditions get a break here too. Under RCW 48.66.130(4), a replacement policy can't apply any pre-existing condition exclusion if the policy it replaces had been in effect for at least three months.

Sequence matters. CMS says not to cancel the old policy until you've decided to keep the new one, and you'll pay both premiums for the month you have both. The OIC is clear that you must cancel the old Medigap once you switch. Use the 30-day window: RCW 48.66.120 lets you return a new policy within 30 days of delivery for a full premium refund, and the returned policy is void from the beginning. The company must also give you an outline of coverage no later than the time you apply (RCW 48.66.110). Read it against your current policy.

Community rating: no price hikes for getting older

CMS describes three ways to price a Medigap policy: community-rated (generally the same premium regardless of age), issue-age (based on your age when you buy) and attained-age (based on your current age, so it rises as you get older).

Washington picked one. RCW 48.66.045(3) requires every Medigap policy issued to a Washington resident since January 1, 1996 to be community-rated: premiums must be equal for everyone under the same standardized plan form. A company may vary premiums only for spousal discounts, how often you pay and how you pay (automatic deposit, for example), and it may keep no more than two rating pools: one for people eligible by age, one for people eligible by disability or end-stage renal disease. WAC 284-66-310 goes further and calls attained-age rating an unfair practice, prohibited outright.

What that doesn't mean: that premiums never go up. They can rise for other reasons, such as medical costs and claims. But a company can't use rates the OIC hasn't approved. RCW 48.66.035(2) says rates and rate changes can't be used until they're filed with and approved by the commissioner. Pair that with the switching right, and a Washington policyholder facing a big increase has more room to move than people in most states.

Your first six months and guaranteed-issue rights

The switching right covers people who already have Medigap. Getting your first policy is a different question, and timing still decides it.

The Medigap Open Enrollment Period. Federal rules give you a one-time, six-month window that starts the first month you have Part B and are 65 or older. It doesn't repeat. During it, a company can't refuse to sell you any policy it offers, can't use medical underwriting and can't charge you more for health problems. Washington's own version is RCW 48.66.025, and under it three months of continuous prior creditable coverage removes any pre-existing exclusion during that window. If you delay Part B because you're covered through current employment, the window starts later. If you got Part B before 65 because of a disability, you get a new open enrollment period at 65.

Outside that window, CMS warns you may pay more, have fewer choices or be turned down by a company that underwrites. The OIC handbook's line that there's no yearly Medigap open enrollment period and you can apply any time is aimed at people already enrolled in a Medigap plan. For a first policy outside your window, without a protected right, the company can ask health questions.

Guaranteed-issue situations. Certain events give you a short right to buy specific Medigap letters with no health questions. Washington's statute is RCW 48.66.055: you must apply no later than 63 days after the coverage ends, and the company can't deny you, charge more for health status or impose a pre-existing condition exclusion. For a voluntary disenrollment, the window starts 60 days before the effective date and ends 63 days after it.

Source: CMS, Choosing a Medigap Policy, 2026, pp. 17-18; RCW 48.66.055. The letters you can buy differ by situation and by when you became eligible; the CMS guide and the Washington statute list them separately.

CMS gives one piece of advice I'd repeat to anyone in these situations: keep copies of the letters, notices, emails or claim denials that show your coverage ended, and keep the postmarked envelope as proof of when it was mailed. The insurer may ask for it.

Under 65 on Medicare in Washington

This is where Washington is weaker than its neighbors. Federal law generally doesn't require companies to sell Medigap to people under 65, and the OIC handbook says Washington doesn't require it either: you can contact insurers directly to see if they'll sell you a policy. CMS's 2026 guide lists 33 states that require at least one kind of Medigap for people under 65. Oregon and Idaho are on that list. Washington isn't.

It affects a lot of people. In June 2026, 127,100 Washington Medicare beneficiaries were under 65 and eligible through disability or ESRD, about 8.0% of the state's 1,583,566 total. People on SSDI are enrolled in Parts A and B automatically after 24 months of benefits, with no wait for ESRD or ALS (OIC).

Two Washington rules still help once you're in:

• The switching right covers you. RCW 48.66.045 applies to people eligible "by reason of age, disability, or end-stage renal disease," so a policy you already hold can be replaced without health questions. Companies may price you in a separate disability/ESRD rating pool.
• You can pause it if you go back to work. WAC 284-66-130(5) requires the application to explain that if you have Medigap because of a disability and later get employer or union group coverage, benefits and premiums can be suspended on request, and reinstated if you ask within 90 days of losing the group plan.

And at 65 you get the full six-month Medigap Open Enrollment Period, even if you've had Part B for years.

Source: CMS Medicare Monthly Enrollment, Washington, June 2026. The A-and-B figure is the group that can generally buy Medigap, not a count of Medigap policyholders.

How many Washingtonians are in Original Medicare

Medigap only pairs with Original Medicare, so the size of that group is the size of the Medigap question. In 2013, 71.4% of Washington's Medicare beneficiaries were in Original Medicare. By 2025 it was 50.8%, and in June 2026 it was 50.3%: 796,152 people in Original Medicare and 787,414 in Medicare Advantage and other health plans.

• Original Medicare
• Medicare Advantage & other

200K400K600K800K1,000K

20132016201920222025

Source: CMS Medicare Monthly Enrollment (annual rows), Washington

Show the numbers

	Original Medicare	Medicare Advantage & other
2013	786K	315K
2014	807K	339K
2015	835K	357K
2016	864K	371K
2017	885K	392K
2018	895K	425K
2019	899K	463K
2020	889K	510K
2021	865K	567K
2022	841K	618K
2023	815K	676K
2024	782K	742K
2025	791K	767K

The two lines nearly meet. Original Medicare's head count barely moved over 12 years while almost all of the growth went to Medicare Advantage. That's a description, not a verdict: the two are built differently, and the right one depends on the person. Just know that the year-round switching right helps people already in Medigap. It doesn't open the door from Medicare Advantage.

Medicare Open Enrollment isn't Medigap enrollment

Medicare Open Enrollment runs from October 15 to December 7, 2026, with changes starting January 1, 2027 (CMS). It's the window to join, drop or switch Medicare Advantage and Part D plans, or to move between Original Medicare and Medicare Advantage (Medicare.gov). It is not a Medigap enrollment period. Medigap has no annual window at all, and the fall season gives no Medigap rights by itself.

Where they meet: if you use this fall to leave Medicare Advantage for Original Medicare, check whether a guaranteed-issue right applies before you count on buying Medigap. I walk through the fall dates in Medicare Open Enrollment 2027 in Washington.

Where to get unbiased help

SHIBA, the Office of the Insurance Commissioner's Medicare counseling program, gives unbiased, confidential Medicare help at no charge. Call 800-562-6900, 8:30 a.m. to 4:30 p.m., Monday through Friday, or start at the SHIBA page. The OIC's one-page chart of the standardized plans and its Medigap handbook are worth printing. Medicare itself is at 1-800-MEDICARE (1-800-633-4227; TTY 1-877-486-2048) and Medicare.gov.

If a company asks health questions when you replace one B-through-N policy with another, the OIC's consumer hotline is the same number. For a general overview of Medicare coverage types in the state, see our Washington Medicare page, and the Washington Medicare Supplement page for how Medigap fits in.

FAQ

Does Washington have a Medigap rule that lets you switch plans?

Yes. Under RCW 48.66.045, someone with a Medigap Plan B through N can switch to another Plan B through N at any time, and Plan A can switch to another Plan A, without health questions. There's no annual window.

Can I get a Medicare Supplement in Washington if I'm under 65?

Washington doesn't require insurers to sell Medigap to people under 65, so you may have to contact companies to see if they'll sell you a policy. Once you have one, the switching right applies, and you get the six-month Medigap Open Enrollment Period at 65.

Do Medigap premiums go up with age in Washington?

Not because of age. Washington requires community rating for policies issued since 1996 and prohibits attained-age rating. Premiums can still change for other reasons, and rate changes must be approved by the Insurance Commissioner first.

Can I change my Medigap plan during Medicare Open Enrollment?

Medicare Open Enrollment, October 15 to December 7, is for Medicare Advantage and Part D. Medigap has no annual window. In Washington, people who already have Medigap can switch under RCW 48.66.045 at any time of year.

Your own policy wording and Washington law control. Confirm your situation with a licensed agent, the Washington Office of the Insurance Commissioner or SHIBA, or, for legal questions, an attorney.

Sources

1. CMS, Choosing a Medigap Policy: A Guide to Health Insurance for People with Medicare, 2026 (Product No. 02110)
2. Medicare.gov: Medigap (Medicare Supplement Health Insurance)
3. Medicare.gov: How Medigap works
4. Medicare.gov: Compare Medigap plan benefits (2026 K/L limits, high-deductible F/G)
5. Medicare.gov: Medicare costs
6. Medicare.gov: Does your provider accept Medicare as full payment? (limiting charge)
7. CMS: 2026 Medicare Parts A & B premiums and deductibles fact sheet (Nov. 14, 2025)
8. CMS: Medicare Open Enrollment 2027 press release (Sept. 2026)
9. Medicare.gov: Joining a plan
10. CMS: Medicare Monthly Enrollment, Washington (annual 2013-2025 and June 2026)
11. RCW 48.66.025: Medigap open enrollment
12. RCW 48.66.035: rate filing and approval
13. RCW 48.66.045: issuance without evidence of insurability; community rating
14. RCW 48.66.055: guaranteed issue for eligible persons
15. RCW 48.66.090: guaranteed renewability
16. RCW 48.66.110: outline of coverage
17. RCW 48.66.120: 30-day return and refund
18. RCW 48.66.130: pre-existing conditions
19. WAC 284-66-064: minimum benefit standards (foreign travel emergency)
20. WAC 284-66-130: required application disclosures (suspension)
21. WAC 284-66-243: rating on a community-rated basis
22. WAC 284-66-310: attained-age rating prohibited
23. WA OIC: Medigap (Medicare Supplement) plan coverage and costs
24. WA OIC/SHIBA: What you need to know about Medigap (Medicare Supplement) plans
25. WA OIC/SHIBA: 10 standardized Medicare Supplement (Medigap) plans chart, 2026
26. WA OIC: Medicare options for people with disabilities
27. WA OIC: SHIBA Medicare help