The decoder ring

Every Medicare term, in plain English.

Fifty terms, defined the way a sharp friend would explain them, with 2026 figures where numbers matter and a link to the article that goes deeper. Bookmark it; the jargon isn’t going anywhere.

A B C D E F G H I L M N O P S T U

A

AEP (Annual Enrollment Period): October 15 to December 7 each year: the window to change Medicare Advantage or Part D plans for January 1. The whole season lives on our open enrollment page.
ANOC (Annual Notice of Change): The September mailing where your plan discloses next year’s premium, deductible, drug tiers, and network changes. Five numbers, ten minutes.
Assignment: A provider “accepts assignment” when they take Medicare’s approved amount as full payment. The magic question to ask any office: “do you accept Medicare assignment?”

B

Benefit period: How Part A counts hospital deductibles: starts at admission, ends after 60 days without inpatient or skilled care. Two stays months apart can mean two $1,736 deductibles in one year.

C

Catastrophic coverage: The Part D phase after you hit the out-of-pocket cap ($2,100 in 2026, $2,400 in 2027): covered drugs cost $0 for the rest of the year.
COBRA: Continuing an employer’s plan after leaving a job. Real insurance, but it does not count as employer coverage for delaying Part B, the single most repeated Medicare mistake.
Coinsurance: Your percentage share of a covered cost. Part B’s is 20%, with no annual cap, which is the number that makes a ceiling non-optional.
Copay: A flat dollar amount per visit or prescription, the pricing style of Advantage plans and Medigap Plan N.
Creditable coverage: Drug coverage at least as good as Part D (most employer plans qualify). Keep every creditable-coverage notice; they’re your proof against the late penalty.
Custodial care: Help with daily living: bathing, dressing, supervision. Medicare never covers it long-term, the hardest truth in the program: the 100-day reality.

D

Deductible: What you pay before coverage engages. 2026: $283 (Part B), $1,736 per benefit period (Part A), up to $615 (Part D, rising to $700 in 2027).
DME (durable medical equipment): Walkers, wheelchairs, CGMs, oxygen: covered under Part B at 80/20 from Medicare-enrolled suppliers.
Donut hole: The old Part D coverage gap, eliminated by the 2025 redesign. If a plan description still mentions it, the description is out of date.
D-SNP: Dual-eligible Special Needs Plan: an Advantage plan built for people with both Medicare and Medicaid, often with the richest supplemental benefits.
Dual eligible: Having Medicare and Medicaid at once, about one in five beneficiaries: Medicare pays first, Medicaid wraps around it.

E

Excess charges: The up-to-15% a non-participating doctor may add above Medicare’s approved amount. Plan G pays them; Plan N doesn’t; eight states ban them.
Extra Help (LIS): The Part D subsidy that pays premiums and deductibles and cuts copays to a few dollars, the most unclaimed money in Medicare.

F

Formulary: A drug plan’s covered-drug list with its tier prices. Formularies change every January, which is why the annual re-shop exists.

G

GEP (General Enrollment Period): January 1–March 31: the catch-up window for Part B if you missed your initial window, with coverage starting the month after enrollment, and penalties intact.
Guaranteed issue: Situations where Medigap insurers must accept you regardless of health: your first 6 months on Part B, plus specific events like plan closures and qualifying moves.

H

High-deductible Plan G: Plan G with a $2,950 deductible (2026) at a fraction of the premium: catastrophic protection for people comfortable self-funding the first layer.
HMO: An Advantage plan type: care inside the network only (emergencies excepted), usually with referrals.

I

IEP (Initial Enrollment Period): Your 7-month window: three months before your birthday month, that month, and three after. The month-by-month checklist.
IRMAA: The income surcharge on Part B and D premiums, based on your tax return from two years ago, starting above $109,000 single / $218,000 joint. The full brackets.

L

Late enrollment penalty: Part B: 10% per 12 months late, permanent. Part D: 1% of the base premium per month, permanent. The exact math.

M

MA OEP: January 1–March 31: Advantage members’ one-switch do-over window. How it works.
MAGI: Modified adjusted gross income: AGI plus tax-exempt interest, the measure IRMAA uses. Roth withdrawals and QCDs don’t count; capital gains and IRA withdrawals do.
Medicare Advantage (Part C): The private-plan path: one bundled plan with networks, copays, an out-of-pocket max, and usually drug coverage. The honest comparison.
Medigap: Supplement insurance that pays Original Medicare’s cost-sharing. Standardized by letter (G and N lead today), compared here.
MOON notice: The written notice hospitals must give within 36 hours when you’re under observation more than 24 hours. If you receive one, read the observation article today.
MSN (Medicare Summary Notice): Your quarterly claims statement on Original Medicare: what was billed, paid, and denied. The scam-detection and appeal-deadline document.
MSP (Medicare Savings Programs): State programs (QMB, SLMB, QI) that pay the Part B premium for people under income limits, and bring automatic Extra Help with them.

N

Network: The providers an Advantage plan covers. Verified only by calling offices with the exact plan name; directories are aspirational.

O

Observation status: Hospital care billed as outpatient: Part B rules, and zero credit toward the 3-day stay skilled nursing requires. The trap and the defense.
Original Medicare: The traditional path: Parts A and B, any doctor who takes Medicare, usually paired with Medigap and a Part D plan.
Out-of-pocket maximum: An Advantage plan’s annual ceiling on your medical cost-sharing, the price of a bad year, and check #3 in plan comparison.

P

Part A: Hospital insurance: inpatient stays, skilled nursing, hospice. Premium-free with ~10 years of covered work. A vs. B, mapped.
Part B: Medical insurance: doctors, outpatient care, equipment. $202.90/month in 2026, $283 deductible, then 80/20.
Part D: Drug coverage through private plans: capped deductible, the out-of-pocket cap, $35 insulin, $0 vaccines.
PDP: A standalone prescription drug plan, paired with Original Medicare. Re-shop yearly; 2027 especially, as subsidies end.
PPO: An Advantage plan type: out-of-network care allowed at higher cost, usually no referrals.
Prior authorization: Plan approval required before certain services, standard in Advantage. A denial is an opening bid: appeals win constantly.

S

SEP (Special Enrollment Period): Life-event windows that reopen enrollment: leaving employer coverage, moving, plan closures, and more. The full catalog.
SHIP: Your State Health Insurance Assistance Program: free, unbiased, commission-free Medicare counseling by phone. The best free phone call in the program.
Skilled care: Care requiring licensed professionals (nursing, therapy), which Medicare covers, versus custodial care, which it doesn’t. The line that decides home health and nursing coverage.
Star ratings: Medicare’s 1–5 quality grades for Advantage and drug plans, refreshed each October. What they measure.

T

TRICARE For Life: Military retirees’ wraparound to Medicare: requires Part B, replaces any need for Medigap. The veterans’ map.
Trial right: Guaranteed return to Medigap if you try Advantage for the first time and leave within the trial period, one of the few open one-way doors.
Two-midnight rule: The standard guiding hospital status: stays expected to span two midnights should generally be inpatient. The sentence to say out loud when observation status threatens.

U

Underwriting: Health-based approval and pricing, which most states allow for Medigap outside protected windows. The reason timing outranks everything in the supplement decision.

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