Your mailbox fills up the minute you turn 64. Every mailer has a reason you need to act right now. Ignore the pressure — but don't ignore the rules. Medicare's enrollment windows are strict, and missing yours can add a penalty to your premium for the rest of your life — not a one-time fee. Here's the honest version: the windows, who must sign up at 65, who can safely wait, and the traps that catch people.
The three doors into Medicare
There are really only three ways into Medicare, and which door you use decides whether you pay a penalty.
- Door 1 — Initial Enrollment Period (IEP). A 7-month window around your 65th birthday: the 3 months before, your birthday month, and the 3 months after. If you need coverage at 65, sign up in the first 3 months so it starts on time.
- Door 2 — General Enrollment Period (GEP). If you miss your IEP and don't qualify for an exception, this is where you land: January 1 – March 31 each year. Coverage starts the month after you enroll — and the lifetime late penalty is now riding on your premium.
- Door 3 — Special Enrollment Period (SEP). If you (or your spouse) are still working with current employer coverage, you can delay Part B penalty-free and use an 8-month window that starts when that job-based coverage ends. COBRA and retiree plans do not count as current employer coverage.
The COBRA trap
This is the one that catches people. COBRA is not "current employer coverage" for Medicare. If you leave your job and lean on COBRA past 65 thinking you're covered, your 8-month special window is already counting down — and when COBRA ends you can be stuck with a gap and a lifetime penalty. If you're 65+ and going on COBRA, talk to Medicare first.
The penalties, in plain numbers
- Part B late penalty: 10% added per full 12 months you could have had Part B but didn't — and it lasts for life. (The standard 2026 Part B premium is $202.90/month, so the penalty stacks on top of that, every month, forever.)
- Part D late penalty: go 63 days or more without creditable drug coverage and you owe roughly 1% × the national base ($38.99 in 2026) × the number of full uncovered months — also for life. The fix is cheap: keep some creditable drug coverage so the clock never starts.
Which one are you?
Most of this comes down to four situations. Find yours:
- Retiring at or before 65 with no other coverage — mark the 7-month window, sign up in the first 3 months, grab a drug plan so the Part D clock never starts, and lock in Medigap during your one-time 6-month window.
- Still working at 65 with real, current employer coverage — you can delay Part B penalty-free. Just confirm it's active-employer coverage, keep your drug coverage creditable, and start the 8-month clock the day the job ends. COBRA does not count.
- Already drawing Social Security — you're auto-enrolled in Parts A and B; watch the mail and keep the card unless you have a specific reason not to.
- Higher income — plan your income two years ahead (see IRMAA below) and file the life-changing-event form if your income dropped.
Two more windows to circle
Annual Election Period — Oct 15 to Dec 7. Switch between Original Medicare and Medicare Advantage, change plans, or join/drop/switch a drug plan, effective January 1. Your plan mails you a notice every fall telling you what's changing next year — read it instead of letting it sit on the counter.
Medicare Advantage Open Enrollment — Jan 1 to Mar 31. If you're already in an Advantage plan, you get one chance to switch to a different Advantage plan or drop back to Original Medicare.
Medigap: the 6-month window that doesn't come back
If you choose Original Medicare, your Medigap Open Enrollment is a one-time 6 months that starts the month you're 65 AND enrolled in Part B. During those six months insurers must sell you any Medigap policy at the best price regardless of your health — that's guaranteed issue. Miss it and you can be medically underwritten, charged more, or turned down. This window is golden; use it.
IRMAA: the penalty for success
One surcharge works the opposite way — it hits you for being successful. If your income is over certain thresholds, IRMAA (the income-related monthly adjustment) adds a surcharge on top of your standard Part B and Part D premiums. The twist: it's based on your tax return from two years ago, so your 2026 premium is set by your 2024 income. A one-time spike — selling a property, a big Roth conversion — can bump you up two years later. It's also a cliff: one dollar over a threshold moves you a whole tier.
The brackets change yearly, so check the current figure at medicare.gov rather than trusting a stale number. Two levers you control: if your income dropped because of a life-changing event (retirement, lost pension, death of a spouse, divorce), file SSA form 44 to use your current income instead; and manage taxable income through the timing of withdrawals and smaller Roth conversions to stay under a line.
Clear the noise — go to the source
The penalties are real, but the rules are public and they don't change based on a phone call from someone who found you first. Handle everything at medicare.gov or, for enrollment, ssa.gov — never a middleman. If a pitch makes you feel panic or reach for your wallet, that's your signal it's bait.
Free 1-page checklist
Every window and every deadline on a single page — the 7-month window, the working-past-65 rule, the penalty math, and the 7-step recap.
Get the checklist→Sources
• CMS — 2026 Medicare Parts A & B premiums & deductibles ($202.90 Part B)
• Medicare.gov — Avoid late enrollment penalties (Part B 10% per 12 mo, for life)
• Medicare.gov — Part D late enrollment penalty (1% × national base; 63-day gap)
• CMS — Original Medicare enrollment periods (IEP, GEP, SEP)
• Medicare.gov — Medicare & You 2026 (handbook)
Educational only — not personal financial, tax, or insurance advice. Everyone's situation is different; confirm your own dates and amounts at medicare.gov, at ssa.gov, by calling 1-800-MEDICARE, or with a licensed professional. Jeffrey Miller is an educator and is not affiliated with or endorsed by Medicare, the SSA, or any government agency.