The Medicare deadline that never forgives you
Almost every date in this decade is negotiable. This one isn’t — miss your enrolment window without the right coverage and you pay a surcharge every month for the rest of your life.
We've written a fair amount on this site about how few of the age thresholds in your 60s actually matter. Most are marketing. Some are openings rather than deadlines.
This is the exception, and it's worth being blunt about it. Medicare's late-enrolment penalties are permanent. Not a one-off fee, not a penalty that expires after a few years — a percentage added to your monthly premium for as long as you have the coverage. Someone who delays Part B by three years without qualifying coverage pays roughly 30% extra every month, for the rest of their life.
The good news is that avoiding it is entirely mechanical. You need to know two things: when your window is, and whether your current coverage exempts you.
Your Initial Enrolment Period
Seven months, centred on the month you turn 65: the three months before, your birthday month, and the three months after.
Enrol in the three months before and coverage generally starts on the first day of your birthday month. Enrol during or after, and it starts later — which can leave a gap. If you have a choice, the early part of the window is the better part.
Your Initial Enrolment Period
Seven months, centred on your birthday month. The early half is the better half.
| $202.90 | Standard monthly Part B premium. Higher earners pay an income-related surcharge, ranging up to $689.90. |
|---|---|
| $283 | Annual Part B deductible. |
| $38.99 | The national base premium used to calculate the Part D late penalty. |
| Part B penalty | 10% added for each full 12-month period you could have had Part B and didn’t. Permanent. |
| Part D penalty | 1% of $38.99 for every full month you went without creditable drug coverage. Permanent, and recalculated annually as the base premium rises. |
| Part A | Free for most people — those with 40 quarters of Medicare-taxed work. That’s why Part A rarely carries a penalty. |
Delay Part D by four years and the penalty is roughly 48% of the base premium — added monthly, permanently, to a bill you'll be paying into your nineties.
The exception that covers most people still working
If you're 65 and still employed — or covered by a spouse's employer plan — you can generally delay Part B without penalty, and pick it up later through a Special Enrolment Period. That's eight months from when the employment or the group coverage ends, whichever comes first.
This is where it goes wrong for people, so read the next paragraph twice.
COBRA and retiree coverage do not count. Neither does severance-continued coverage. The exemption requires coverage based on current, active employment. Someone who retires at 64, takes 18 months of COBRA and assumes they're protected is accumulating penalty months the entire time — and typically discovers it years later, when there is nothing to be done about it.
One further wrinkle if your employer is small: with fewer than 20 employees, Medicare usually becomes the primary payer at 65, and the group plan pays second. Delaying Part B in that situation can leave you with far less coverage than you think you have. Ask your benefits administrator directly whether the plan is primary or secondary once you turn 65. It's a short question with a large consequence.
The HSA trap
A specific one that catches organised people, because it punishes planning ahead.
You cannot contribute to a health savings account once you're enrolled in any part of Medicare. And when you enrol in Part A after 65, coverage is applied retroactively — up to six months back, though never before your 65th birthday month.
So contributions made during those retroactive months become excess contributions, with tax consequences attached. If you're working past 65 and funding an HSA, stop contributing about six months before you plan to enrol. Note also that claiming Social Security automatically enrols you in Part A, which means the Social Security decision and the HSA decision are quietly linked.
If you’ve already missed it
Not ideal, but not hopeless. The General Enrolment Period runs 1 January to 31 March each year, and since 2023 coverage begins the month after you sign up rather than waiting until July. The penalty still applies, but the gap in coverage is much shorter than it used to be.
It's also worth knowing that penalties can be waived if you were misled by a government representative, and that they don't apply at all if you qualify for Extra Help. Both are worth raising rather than assuming.
What to actually do
- Find your window: count three months back from your 65th birthday month, and put that date in a calendar now. Not a mental note.
- Still working? Ask your benefits administrator two questions: is this coverage based on current employment, and is it primary or secondary once I turn 65?
- Never rely on COBRA or retiree coverage to protect you from the Part B penalty. It doesn’t.
- Check whether your drug coverage is creditable — your plan must tell you in writing each year. Keep those letters; they’re your evidence if a penalty is ever assessed wrongly.
- Funding an HSA past 65? Stop about six months before you enrol.
- Talk to your SHIP — the State Health Insurance Assistance Program. Free, unbiased, one per state, and they are not selling you a plan. Reach them via shiphelp.org or 1-800-MEDICARE.
Nearly everything else in this decade can be revisited. Claim Social Security early and you can sometimes withdraw or suspend. Choose the wrong Part D plan and you can change it in the autumn. Buy the wrong house and you can sell it.
This one doesn't work that way. Which is why, of all the dates on this site, it's the one worth writing down today.
This is general information, not personal advice. We report the rules, the numbers and the deadlines as clearly as we can. We don't know your income, your state, your health or your family — and all four can change the answer. Treat this as a good place to find the right questions, not a substitute for someone looking at your actual situation.
Where these facts come from
Checked against primary sources on 10 August 2026. Dollar limits and program rules change — if you're reading this well after that date, verify the numbers at the links below.
- Medicare — Avoid late enrolment penalties — https://www.medicare.gov/basics/costs/medicare-costs/avoid-penalties
- Medicare — When does Medicare coverage start? — https://www.medicare.gov/basics/get-started-with-medicare/sign-up/when-does-medicare-coverage-start
- CMS — 2026 Medicare Parts A & B premiums and deductibles — https://www.cms.gov/newsroom/fact-sheets/2026-medicare-parts-b-premiums-and-deductibles
- SHIP — Free local Medicare counselling — https://www.shiphelp.org/
Edward Silva
Edward spent more than forty years as a computer professional — long enough to pick up one useful occupational habit: when somebody hands you a summary, go and read the actual documentation. He started The Second Half Guide after noticing that most writing aimed at people his age was either talking down to him or quietly selling him something, and that the plain facts — the dates, the thresholds, the dollar figures — were somehow the hardest part to find.
He's married, with two grown sons, both married themselves. He is not a financial adviser, an attorney or an insurance agent, and this site doesn't tell you what to do with your money. It tells you what the rules actually say, and links to where he checked.