Enrolling in Medicare without penalties
Medicare's biggest risk isn't picking the wrong plan — it's missing an enrollment window and triggering a penalty that follows you for life. This page covers the parts, the windows, and the "am I still working" question that trips up more people than anything else.
01 Six steps to enrolling correctly
| Part | Covers | 2026 cost snapshot |
|---|---|---|
| Part A — Hospital | Inpatient hospital stays, skilled nursing, hospice, some home health | Usually premium-free if you (or a spouse) paid Medicare taxes for 10+ years; $1,736 deductible per benefit period |
| Part B — Medical | Doctor visits, outpatient care, preventive services, durable medical equipment | $202.90/month standard premium (income-adjusted), $283 annual deductible, then typically 20% coinsurance |
| Part C — Medicare Advantage | A private-plan alternative that bundles Parts A + B (usually D too), often with extra benefits like dental/vision/hearing | Premiums vary by plan; uses a network, unlike Original Medicare |
| Part D — Prescription drugs | Outpatient prescription drugs, via a standalone plan or bundled into Medicare Advantage | Premiums vary by plan (income-adjusted) |
There's also Medigap (Medicare Supplement) — optional private insurance that only works alongside Original Medicare (A+B), designed to cover the ~20% coinsurance Part B leaves you owing. It's cheapest and easiest to get within 6 months of starting Part B, when insurers must sell it to you regardless of health (guaranteed issue) — after that window, they can medically underwrite you in most states.
Your Initial Enrollment Period (IEP) is a 7-month window centered on your 65th birthday: the 3 months before, your birthday month, and the 3 months after.
- Enroll in the first 3 months and coverage starts the month you turn 65.
- Enroll during your birthday month or the 3 months after and coverage starts the month after you sign up — so waiting inside your own IEP can still cost you a coverage gap.
This is the single most common Medicare mistake. The answer depends entirely on your employer's size.
| Your situation | What to do |
|---|---|
| Employer has 20 or more employees, you're actively working, and covered by that group plan | You can delay Part B (and Part A, if you'd owe a premium) without penalty. The employer plan pays first; Medicare would be secondary if you had it. |
| Employer has fewer than 20 employees | Medicare becomes primary at 65 regardless of work status — you generally need to enroll in both A and B at 65 to avoid coverage gaps, since the small-employer plan will assume Medicare is paying first. |
| You're on COBRA or retiree coverage (not active employment) | Neither counts as creditable coverage for delaying Part B. Enroll in Medicare at 65 on schedule. |
When qualifying employer coverage ends, an 8-month Special Enrollment Period (SEP) opens, starting the month after employment or the coverage ends, whichever is first. Enroll within that window and you avoid the late penalty.
| Part | Penalty | Duration |
|---|---|---|
| Part B | +10% of the standard premium for each full 12-month period you were eligible but not enrolled (and lacked creditable coverage) | For as long as you have Part B — potentially for life |
| Part D | +1% of the national base premium for each month without creditable drug coverage | For as long as you have Part D — potentially for life |
| Part A (if you owe a premium) | +10% for twice the number of years you delayed | Limited duration (not for life) |
"Creditable coverage" means health or drug coverage that's at least as good as Medicare's — active employer coverage from a large employer qualifies; COBRA and most retiree plans do not count for Part B purposes (though retiree drug coverage often does count for Part D).
If your income is above certain thresholds, you pay more for Part B and Part D — this surcharge is called IRMAA (Income-Related Monthly Adjustment Amount). It's based on your Modified Adjusted Gross Income from your tax return two years prior — your 2026 premium is based on your 2024 return.
2026 IRMAA brackets (Part B, monthly)
| Single filer MAGI | Married filing jointly MAGI | Monthly Part B |
|---|---|---|
| $109,000 or less | $218,000 or less | $202.90 (standard) |
| Up to $137,000 | Up to $274,000 | ~$284 |
| Up to $171,000 | Up to $342,000 | ~$406 |
| Up to $205,000 | Up to $410,000 | ~$528 |
| Under $500,000 | Under $750,000 | ~$649 |
| $500,000+ | $750,000+ | ~$690 |
Part D carries a comparable surcharge on top of your plan's own premium, using the same income brackets.
| Window | Dates | What you can do |
|---|---|---|
| Annual Enrollment Period (AEP) | Oct 15 – Dec 7 | Switch Medicare Advantage or Part D plans for the following year |
| Medicare Advantage Open Enrollment | Jan 1 – Mar 31 | If already in a Medicare Advantage plan, switch to a different one or back to Original Medicare (once) |
| General Enrollment Period (GEP) | Jan 1 – Mar 31 | Enroll in Part B if you missed your IEP and don't qualify for a Special Enrollment Period — coverage starts the month after you enroll, but late penalties likely apply |