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Medigap glossary

By Vadim Marusin, licensed Medicare insurance agent in Washington (WAOIC #1365574). Insurer data checked against the state chart current as of October 8, 2026.

Plain definitions of the terms you'll see when buying Medicare Supplement insurance in Washington, with the Washington-specific rules noted.

Assignment

A provider's agreement to accept Medicare's approved amount as full payment. Providers who accept assignment can't bill Part B excess charges.

Attained-age rating

Pricing that raises a Medigap premium as you get older. Not allowed in Washington.

Benefit period

How Medicare measures hospital and skilled nursing use. It starts when you're admitted and ends after 60 days in a row without inpatient or skilled care. The Part A deductible applies to each benefit period.

Community rating

Pricing that charges everyone in a plan the same premium regardless of age. Washington requires it for Medigap (RCW 48.66.045).

Coinsurance

Your percentage share of a cost, such as Medicare Part B's 20%.

Copay

A fixed dollar amount you pay for a service, such as Plan N's up-to-$20 office visit copay.

Creditable coverage

Health or drug coverage that counts toward avoiding late penalties or shortening Medigap waiting periods.

Crossover

Automatic forwarding of a claim from Medicare to your Medigap insurer, so you rarely file Medigap claims yourself.

Excess charge

The amount, up to 15% over Medicare's approved amount, that a provider who doesn't accept assignment can bill you. Plans F and G pay it.

Free look

Washington's 30-day period to return a new Medigap policy for a full refund (RCW 48.66.120).

Guaranteed issue

A situation where an insurer must sell you a Medigap policy without health questions, such as losing employer coverage.

Guaranteed renewable

The insurer must renew your Medigap policy as long as you pay the premium and your application was truthful.

High-deductible plan

Plan G or F with a yearly deductible ($2,950 in 2026) before the plan pays.

Household discount

A premium discount when a spouse or partner has a policy with the same insurer; one of the few discounts Washington allows.

IRMAA

Income-related monthly adjustment amount: extra Part B and Part D premiums for people above certain incomes.

Issue-age rating

Pricing based on your age when you buy. Not allowed in Washington.

Lifetime reserve days

60 extra Medicare hospital days you can use once in your lifetime after day 90 of a benefit period. Every Medigap plan covers their coinsurance.

Limiting charge

The most a provider who doesn't accept assignment can charge: 115% of Medicare's approved amount.

Medicare Advantage (Part C)

Private plans that replace Original Medicare. Medigap doesn't work with them.

Medicare SELECT

A Medigap policy that requires network hospitals for non-emergency care in exchange for a lower premium. Sold in Washington by UnitedHealthcare (AARP).

Medigap

Medicare Supplement insurance: private policies that pay costs Original Medicare doesn't, standardized by letter.

Open enrollment (Medigap)

Your one-time six-month window, starting when you're 65 and enrolled in Part B, when insurers must accept you.

Original Medicare

The federal program: Part A (hospital) and Part B (medical). Medigap supplements it.

Outline of coverage

The standardized summary every insurer must give you before you buy, listing benefits, exclusions and renewal terms.

Part A

Medicare hospital insurance: inpatient stays, skilled nursing, hospice, some home health.

Part B

Medicare medical insurance: doctors, outpatient care, tests, equipment and preventive services.

Part D

Medicare prescription drug coverage, bought separately from Medigap.

Pre-existing condition waiting period

Time a policy may refuse to pay for a condition treated before coverage started. Washington caps it at three months.

Rate increase

An approved change to a Medigap premium that applies to everyone in the plan. Filed with Washington's Office of the Insurance Commissioner.

SHIBA

Statewide Health Insurance Benefits Advisors, Washington's free Medicare counseling program, 1-800-562-6900.

Skilled nursing facility coinsurance

The daily amount ($217 in 2026) for days 21 to 100 of a Medicare-covered skilled nursing stay.

Standardized plans

The lettered Medigap plans (A, B, C, D, F, G, K, L, M, N) whose benefits are set by federal law.

Switching rule (Washington)

Washington's rule letting people with Medigap Plan B through N switch to another Plan B through N any time without health questions; Plan A to Plan A.

Trial right

The right to return to Original Medicare and buy Medigap without health questions within 12 months of first trying Medicare Advantage.

Underwriting

An insurer's review of your health answers to decide whether to accept you, outside protected windows.

WSHIP

Washington State Health Insurance Pool, which offers a Medicare Supplement plan to some people declined by Medigap insurers.