Turning 65: Your Medicare Enrollment Timeline, Month by Month
Part of our health insurance and Medicare basics guide. Medicare does not wait for you to be ready. Your first sign-up window opens three months before your 65th birthday month and closes three months after it. This page explains each step of that window, when coverage actually starts, what the late penalties cost and the main exception for people still working.
Everything here comes from Medicare.gov. It is general information, not enrollment advice. For help with your own dates, contact your State Health Insurance Assistance Program (SHIP) at shiphelp.org or use Medicare.gov's eligibility tools.
Key takeaways
- The Initial Enrollment Period lasts 7 months, centered on the month you turn 65.
- Sign up before your birthday month and Part B starts the month you turn 65. Sign up later in the window and it starts the month after you sign up.
- Part B's late penalty is 10% for each full 12 months you went without it, usually for as long as you have Part B.
- If you still have job-based coverage, you may get an 8-month Special Enrollment Period instead. COBRA and retiree coverage do not count.
When does the Medicare Initial Enrollment Period start and end?
Medicare.gov defines your first chance to sign up as the Initial Enrollment Period: it "lasts for 7 months, starting 3 months before you turn 65, and ending 3 months after the month you turn 65."
If your 65th birthday is in July, the window runs from April through October. Medicare.gov adds one wrinkle: if your birthday is on the first of the month, coverage starts the month before you turn 65, which shifts your dates back one month. Medicare.gov's eligibility tool gives your exact window.
Do you have to sign up, or is it automatic?
It depends on Social Security. Medicare.gov says that if you will get retirement or disability benefits from Social Security at least 4 months before you turn 65, you get Part A and Part B automatically when you turn 65. Everyone else signs up through Social Security.
When does Medicare coverage start if you sign up during the window?
Medicare.gov says coverage "always starts on the first of the month." The month depends on when you sign up.
| If you sign up | Part B (and premium-Part A) starts | Example: July birthday |
|---|---|---|
| Before the month you turn 65 | The month you turn 65 | Sign up in April, May or June: starts July 1 |
| The month you turn 65 | The next month | Sign up in July: starts August 1 |
| In the 3 months after | The next month | Sign up in September: starts October 1 |
Premium-free Part A follows its own rule: Medicare.gov says it starts 6 months back from when you sign up, but no earlier than the month you turn 65. If you sign up during the 7-month window, that works out to the month you turn 65.
The practical point: signing up in the first three months avoids a gap between your 65th birthday and your coverage.
What happens if you miss your Initial Enrollment Period?
You wait, and you may pay more. After the Initial Enrollment Period, Medicare.gov says you can sign up for Part B during the General Enrollment Period, "between January 1-March 31 each year," with coverage starting the month after you sign up. You may owe a late penalty unless you qualify for a Special Enrollment Period.
How much is the Medicare late enrollment penalty?
Medicare.gov stresses that late penalties "are not a one-time late fee." They are added to your monthly premium and usually last as long as you have that coverage.
| Part | Penalty rule (Medicare.gov) | How long it lasts |
|---|---|---|
| Part A (only if you must buy it) | Premium may go up 10% | Twice the number of years you did not sign up |
| Part B | Extra 10% for each full 12-month period you could have had Part B | Usually as long as you have Part B |
| Part D (drug coverage) | 1% of the national base beneficiary premium for each month without creditable coverage | As long as you have Medicare drug coverage |
Medicare.gov's own 2026 worked examples:
- Part B, 24 months late: a 20% penalty. $202.90 standard premium plus $40.58 (20% of $202.90) equals $243.48, which Medicare rounds to $243.50 a month for 2026.
- Part D, 14 months late: a 14% penalty on the $38.99 national base beneficiary premium. $38.99 times 0.14 equals $5.46, rounded to $5.50 a month on top of the plan's premium for 2026.
When the Part D penalty applies: Medicare.gov says the drug penalty applies if you go 63 days or more without creditable drug coverage after your Initial Enrollment Period. Ask your employer or plan in writing whether your current drug coverage is creditable.
Can you delay Medicare if you are still working at 65?
Often, yes. If you have health insurance through your current job or your spouse's current job, Medicare.gov lists a Special Enrollment Period for Part A and Part B. It starts after your Initial Enrollment Period and "ends 8 months after the group health plan coverage or the employment ends, whichever happens first." Signing up during it generally avoids the Part B penalty.
Two traps, both stated plainly by Medicare.gov:
- "COBRA isn't considered group health plan coverage," and "getting COBRA doesn't change when this Special Enrollment Period ends." If you leave a job and take COBRA, the 8-month clock is still running.
- These situations do not qualify for a Special Enrollment Period: your COBRA or retiree coverage ending, missing the 8-month window, or having or losing Marketplace coverage.
If you are leaving a job near 65, read our guide to health insurance options after losing your job alongside this one. The deadlines overlap.
What comes after Part A and Part B?
Signing up for Part A and Part B is step one. The next choice is how you take your coverage: Original Medicare, with or without a Medigap policy, or a Medicare Advantage plan. Our comparison of Medigap vs Medicare Advantage basics explains the differences without recommending either.
Timing matters here too. Your Medigap Open Enrollment Period starts the first month you have Part B and are 65 or older, and Medicare.gov calls it "a one-time enrollment period." If you delay Part B because you are still working, that 6-month Medigap window is delayed with it. A few states add an annual window for people who already have Medigap; see our list of Medigap birthday rule states.
For drug and Medicare Advantage plans, Medicare.gov says that if you joined a Medicare Advantage plan during your Initial Enrollment Period, you can change plans or go back to Original Medicare within the first 3 months you have Part A and Part B.
A simple checklist for the months before 65
- Three to four months before your birthday month, check whether you will be enrolled automatically through Social Security.
- If you have job-based coverage, ask your employer whether it is group health plan coverage based on current employment and whether its drug coverage is creditable.
- Decide whether to sign up before your birthday month so Part B starts on time.
- Note your Medigap Open Enrollment Period dates if you plan to stay in Original Medicare.
- Contact your SHIP for a free review of your dates.
FAQ
Can I sign up for Medicare online? Yes, for many people. Medicare.gov links to Social Security's online application for Part A and Part B, and to a Part B-only application if you already have Part A.
What if my birthday is on the first of the month? Medicare.gov says coverage then starts the month before you turn 65, which moves your dates one month earlier. Use Medicare.gov's eligibility tool to confirm.
Is the Part B penalty permanent? Medicare.gov says penalties are usually charged for as long as you have that type of coverage, which for most people means a lifetime penalty. The Part A penalty is the exception: it lasts twice the number of years you did not sign up.
Does Marketplace coverage let me delay Part B without a penalty? No. Medicare.gov lists having or losing Marketplace coverage among situations that do not qualify for a Special Enrollment Period.
I have an HSA. Does that change anything? It can. Medicare.gov flags HSA accounts as a special case on its coverage start page because Part A can start up to 6 months back from when you sign up. Check with your HSA administrator and Medicare.gov before you enroll.
Sources
- Medicare.gov, "When does Medicare coverage start?", accessed October 1, 2026. https://www.medicare.gov/basics/get-started-with-medicare/sign-up/when-does-medicare-coverage-start
- Medicare.gov, "Avoid late enrollment penalties," accessed October 1, 2026. https://www.medicare.gov/basics/costs/medicare-costs/avoid-penalties
- Medicare.gov, "I'm getting Social Security benefits before 65," accessed October 1, 2026. https://www.medicare.gov/basics/get-started-with-medicare/before-65
- Medicare.gov, "Joining a plan," accessed October 1, 2026. https://www.medicare.gov/basics/get-started-with-medicare/get-more-coverage/joining-a-plan
- Medicare.gov, "Get ready to buy" (Medigap), accessed October 1, 2026. https://www.medicare.gov/health-drug-plans/medigap/ready-to-buy
- SHIP Technical Assistance Center, "Get Medicare Help from Your Local SHIP Program," accessed October 1, 2026. https://www.shiphelp.org/
This page is general information, not enrollment, insurance or legal advice. FinanceRazor does not sell or recommend Medicare plans. Confirm your dates with Medicare.gov, Social Security or your State Health Insurance Assistance Program.