When can I sign up for Medicare?
Your first chance is called the Initial Enrollment Period. The chart shows the seven months for someone who turns 65 on July 15, 2027, and when Part B coverage starts for each sign up month.
- April 2027: window opensThree months before your birthday month. Sign up now and Part B starts July 1.
- May 2027Sign up and Part B still starts July 1.
- June 2027Last month to sign up and have Part B start July 1.
- July 2027: your birthday monthPremium-free Part A starts July 1 if you qualify. Sign up for Part B this month and it starts August 1.
- August 2027Sign up and Part B starts September 1.
- September 2027Sign up and Part B starts October 1.
- October 2027: window endsLast month of the window. Part B starts November 1. After this you wait for the General Enrollment Period and may pay a penalty.
Source: Medicare.gov, When does Medicare coverage start?
When does my coverage start?
Part B starts the month you turn 65 if you sign up in one of the 3 months before it. If you sign up in your birthday month or the 3 months after, it starts the next month. Premium-free Part A starts the month you turn 65. Coverage always starts on the first day of a month.
| If you | Coverage starts | Example: you turn 65 on July 15, 2027 |
|---|---|---|
| Sign up for Part B before the month you turn 65 | The month you turn 65 | Sign up in April, May or June: July 1, 2027. |
| Sign up for Part B in the month you turn 65 or in the 3 months after | The next month | Sign up in July: August 1. In October: November 1. |
| Qualify for premium-free Part A | The month you turn 65. If your birthday is on the first, the month before. | July 1, 2027. |
| Sign up for premium-free Part A later | Up to 6 months back, but no earlier than the month you turned 65 | Sign up in March 2028: coverage goes back to September 2027. |
| Miss your window and sign up between January 1 and March 31 | The month after you sign up | A late enrollment penalty may apply. |
If your birthday is on the first of a month, Medicare counts you as turning 65 in the month before, so every date in the chart and table moves one month earlier.
Do I have to sign up myself?
It depends on Social Security. If you get Social Security or Railroad Retirement Board benefits at least 4 months before you turn 65, you are enrolled in Part A and Part B automatically. Your Medicare card arrives in a welcome package about three months before coverage starts. Otherwise you sign up yourself.
- Online at the Social Security website.
- By phone at 1-800-772-1213 (TTY 1-800-325-0778).
- At your local Social Security office.
If you are enrolled automatically, you can still turn down Part B if you have other coverage that you want to keep. Check first, because waiting can mean a penalty later.
What if I am still working at 65?
You may be able to wait on Part B without a penalty if you or your spouse are still working and have health coverage through that job. When the job or the coverage ends, whichever happens first, you get an 8 month Special Enrollment Period to sign up.
- COBRA and retiree coverage do not count. Choosing COBRA does not change when your 8 month window ends.
- Employer size matters. At an employer with 20 or more employees, your job plan usually pays first, so you can usually wait on Part B. At a smaller employer, Medicare usually pays first, so waiting can leave you with gaps. Ask your benefits office before you delay.
- If you have a health savings account, you cannot contribute once Medicare starts, and Part A can start up to 6 months back. Stop contributing earlier than your sign up date.
What do I do about my marketplace plan?
If you will soon have Medicare Part A or Medicare Advantage, end your marketplace coverage. It does not end by itself. You can report a Medicare start date on your marketplace application up to 3 months before Medicare starts.
Once you are eligible for premium-free Part A, you cannot get savings on a marketplace plan. If you keep the plan and use the premium tax credit, you will have to pay the credit back when you file your taxes.
Medicare has its own tools to lower costs and add coverage, including drug coverage, so review those before you cancel anything.
What happens if I miss my window?
You can sign up for Part B only from January 1 to March 31 each year, in the General Enrollment Period, unless you qualify for a Special Enrollment Period. Coverage then starts the month after you sign up. You may pay a late enrollment penalty for as long as you have Part B, and it grows the longer you wait.
Medicare Open Enrollment, October 15 to December 7, 2026, is a different period. It is for changing plans if you already have Medicare, not for signing up for the first time.
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