When to sign up for Medicare

Education, not advice. This guide explains general rules with invented examples. It isn't financial, tax or legal advice for your situation. Tax figures are for 2026 and come from published IRS, SSA and CMS sources. Rules change, so check current figures before you act.

Medicare starts at 65 for most people, whatever age you claim Social Security. Signing up on time matters. Miss your window without other qualifying coverage, and you can pay a higher premium for the rest of your life, and go months without coverage.

This guide covers when to enroll, when it's safe to wait, and the mistakes that cost money.

The parts of Medicare

Part A covers hospital stays. Most people pay no premium for it, because they or a spouse paid Medicare taxes while working.
Part B covers doctors and outpatient care. In 2026, the standard premium is $202.90 a month, and the yearly deductible is $283.
Part D covers prescription drugs, through private plans.
Medigap policies help pay what Parts A and B leave to you. Medicare Advantage plans replace Parts A, B and usually D with one private plan.

Higher incomes pay more for Parts B and D. See IRMAA and ACA subsidy cliffs.

Your initial enrollment period

Your first chance to sign up is a seven-month window around your 65th birthday:

the three months before the month you turn 65
the month you turn 65
the three months after

Sign up in the three months before, and coverage starts on the first day of your birthday month. Sign up in your birthday month or later, and coverage starts the month after you sign up. Signing up early in the window avoids a gap.

If you already receive Social Security, you're enrolled in Parts A and B automatically. Your card arrives before your birthday month. You can turn down Part B if you have qualifying coverage from current work.

If you don't receive Social Security yet, you must sign up yourself, through Social Security.

When you can wait: coverage from current work

You can delay Part B without a penalty if you, or your spouse, are still working and covered by that employer's group health plan. When the job or the coverage ends, whichever comes first, you get an eight-month special enrollment period to sign up.

Two details catch people out:

Only coverage from current work counts. COBRA and retiree health plans don't. If you rely on them past your initial window, you can face a penalty and a gap.
Small employers are different. If the employer has fewer than 20 employees, Medicare usually pays first at 65. You generally need Parts A and B to be fully covered, even while working.

Many people still take Part A at 65 while working, because it's usually free. If you contribute to a health savings account, read the next section first.

Health savings accounts and Medicare

You can't contribute to an HSA once you're enrolled in any part of Medicare. That includes Part A.

There's a trap. When you sign up for Part A after 65, coverage is backdated up to six months, but not before the month you turned 65. Contributions made during those backdated months are excess contributions. Stop HSA contributions about six months before you plan to enroll.

Starting Social Security after 65 also enrolls you in Part A automatically, with the same backdating. You can still spend your HSA on qualified medical costs, including Medicare premiums. See the HSA in retirement.

The late-enrollment penalties

Part B

If you sign up late without qualifying coverage, your Part B premium rises. It goes up 10% for each full 12-month period you could have had Part B but didn't. You pay it for as long as you have Part B.

Late sign-ups outside a special period also have to wait. The general enrollment period runs from January 1 to March 31. Coverage starts the month after you sign up.

Part D

If you go 63 days or more without Part D or other creditable drug coverage, you pay a penalty for life. It's 1% of the national base beneficiary premium for each month without coverage. In 2026 that base premium is $38.99 a month. Employer drug coverage usually counts as creditable, and the plan tells you each year whether it does.

A worked example

Rita turned 65 and retired, moving onto her former employer's retiree health plan. She assumed that let her delay Medicare. It didn't, because retiree coverage isn't coverage from current work. She signed up for Part B 30 months after her initial window ended.

Part B penalty. Thirty months contains two full 12-month periods, so her premium rises 20%. At the 2026 standard premium, that's about $40.60 more each month, for life.
Part D penalty. Her retiree plan's drug coverage was creditable, so she owes no Part D penalty.
A coverage gap. She signed up in February, during the general enrollment period. Her Part B coverage started in March.

Over 20 years of retirement, a 20% Part B surcharge costs thousands of dollars, and it rises as premiums rise.

Compare Rita's colleague Omar, who also retired at 65. He signed up for Parts A, B and D two months before his birthday. His coverage started on time, with no penalty.

Medigap: the six-month window

Your Medigap open enrollment period lasts six months. It starts in the first month you're both 65 or older and enrolled in Part B. During it, insurers must sell you any Medigap policy they offer, at their standard price, whatever your health.

After the window, insurers in most states can charge more or turn you down based on your health. If you're choosing between Medigap and Medicare Advantage, this window is one reason to decide carefully at 65.

Income at 63 sets premiums at 65

Medicare's income surcharges use your tax return from two years earlier. Your premiums at 65 depend on your income at 63. A large Roth conversion, home sale or final bonus at 63 can raise your first Medicare premiums.

If your income dropped because you stopped working, Social Security can use a more recent year. You ask for that with a life-changing event request.

How the app handles Medicare

The plan assumes each person moves to Medicare at 65. Before 65, after retiring, it uses the coverage you choose: a marketplace plan with the premium tax credit, another plan, or none. While someone is still working toward retirement, the plan assumes employer coverage.

From 65, the plan adds the Part B premium and, if you include it, Part D from the current Medicare figures. Surcharges use your plan's income from two years earlier. You add your Medigap or Medicare Advantage premium and out-of-pocket costs, which grow at your healthcare inflation rate.

The app doesn't calculate late-enrollment penalties. If you expect one, add it as a healthcare expense.

Frequently asked questions

No. They're separate. You can start Medicare at 65 and delay Social Security to 70.

My spouse is younger. Can they stay on my work plan?

Medicare covers individuals, not couples. If your spouse is under 65 and you leave a job, they'll need their own coverage until 65. See retiring before 65.

Can I change plans later?

Each fall, during open enrollment, you can switch Part D plans or move between original Medicare and Medicare Advantage. Moving from Medicare Advantage back to Medigap later may need health questions.