Your Medicare Initial Enrollment Period is 7 months long. It starts 3 months before the month you turn 65, includes your birthday month, and ends 3 months after it. If you sign up before your birthday month, Part B coverage starts the month you turn 65. Missing this window without other qualifying coverage can mean a late enrollment penalty that lasts as long as you have Medicare.
Your 7-month Initial Enrollment Period
Think of it as a window that opens 3 months before your 65th birthday month and closes 3 months after it.
| When you sign up | When Part B coverage starts |
|---|---|
| Any of the 3 months before your birthday month | The first day of your birthday month |
| During your birthday month | The first day of the next month |
| Any of the 3 months after your birthday month | The first day of the month after you sign up |
Premium-free Part A starts the month you turn 65. If your birthday falls on the first of the month, Medicare treats you as turning 65 the month before, so every date above moves one month earlier.
Example: If you turn 65 on July 18, your window runs April through October. Sign up in April, May, or June and Part B starts July 1.
Automatic or not?
If you are already collecting Social Security retirement benefits when you turn 65, Medicare usually enrolls you in Part A and Part B automatically. Your card shows up in the mail about 3 months before your birthday.
If you are not collecting Social Security yet, nothing happens on its own. You sign up through Social Security, online at ssa.gov, by phone at 1-800-772-1213, or in person at a Social Security office. In the Santa Clarita Valley, the closest office is on Tourney Road in Valencia.
If you are still working at 65
This is where people get tripped up. If you or your spouse are actively working and covered by an employer group health plan, you may be able to delay Part B without a penalty. When that coverage ends, you get an 8-month Special Enrollment Period to sign up.
Three things to know before you delay:
- Employer size matters. With smaller employers, Medicare often pays first, which means you may need Part B at 65. Ask your benefits administrator how your plan works with Medicare.
- COBRA and retiree coverage do not count the same way as active employment coverage for delaying Part B.
- Health savings accounts. Once you are enrolled in any part of Medicare, you can no longer contribute to an HSA. Talk with your tax advisor about timing.
The big choice: two paths
Once you have Part A and Part B, you choose how you want to receive the rest of your coverage. Broadly, there are two paths:
- Original Medicare plus extras. Keep Original Medicare, add a stand-alone Part D drug plan, and consider a Medicare Supplement (Medigap) policy to help with the costs Original Medicare does not cover.
- Medicare Advantage. Get your Part A and Part B benefits through a private plan approved by Medicare. Most include drug coverage. You generally use the plan's network of doctors and hospitals.
Neither path is right for everyone. Your doctors, your prescriptions, how much you travel, and how you feel about predictable costs versus lower premiums all matter. I walk through both side by side in Medicare Advantage vs. Medigap.
The Medigap window you only get once
If you are leaning toward Original Medicare with a Medigap policy, pay attention to timing. Your Medigap Open Enrollment Period lasts 6 months and starts the first month you have Part B and are 65 or older. During those 6 months, a company cannot use your health history to turn you down or charge you more. After that, health questions can apply. California adds some extra protections, which I cover in Medigap in California.
Your turning-65 checklist
- Write down your Initial Enrollment Period dates.
- Decide whether you need Part B now or qualify to delay it, and get that answer in writing from your employer.
- Sign up through Social Security if you are not enrolled automatically.
- List your doctors, medical group, hospital, pharmacy, and every prescription.
- Decide on Original Medicare plus extras, or Medicare Advantage.
- Make sure you have drug coverage or other creditable coverage, so you avoid the Part D penalty.
- Keep every letter Medicare and Social Security send you.
Common questions
When should I sign up for Medicare if I am turning 65?
If you are not already getting Social Security benefits, the cleanest move is usually to sign up in the 3 months before your birthday month. That way Part B starts the month you turn 65 and there is no gap.
Will I be signed up automatically?
If you already get Social Security retirement benefits when you turn 65, you are generally enrolled in Part A and Part B automatically and your card arrives in the mail. If you are not getting Social Security yet, you have to sign up yourself, usually online at ssa.gov, by phone, or at a Social Security office.
I am still working. Do I need Part B at 65?
It depends on your employer coverage. If you or your spouse are actively working and covered by a group health plan, many people can delay Part B without a penalty and use a Special Enrollment Period later. The size of the employer matters. Talk to your benefits administrator before you decide, and keep written proof of your coverage.
What is the Part B late enrollment penalty?
If you do not sign up for Part B when you are first eligible and you do not have qualifying coverage, your Part B premium can go up 10% for each full 12-month period you could have had Part B but did not. In most cases you pay that penalty for as long as you have Part B.
What is the Part D late enrollment penalty?
If you go 63 days or more in a row without Part D or other creditable drug coverage after your Initial Enrollment Period ends, a late penalty can be added to your Part D premium. It is based on how many months you went without coverage, and you generally pay it for as long as you have Part D.
When can I buy a Medigap policy without health questions?
Your Medigap Open Enrollment Period lasts 6 months and starts the first month you have Part B and are 65 or older. During that time, a company cannot use your health to turn you down or charge you more. After it ends, health questions can apply.
Where these facts come from: Medicare.gov: when does Medicare coverage start, Part B and Part D late enrollment penalties; Social Security Administration. Rules and dollar amounts change. Page reviewed October 4, 2026.