Enter your date of birth to see your 7-month Initial Enrollment Period, the date coverage starts for each sign-up month, and the deadlines that come after it. Working past 65 or signing up late? Add those details to check your Special Enrollment Period and any Part B late penalty.
Last updated:
About you
Started at least 4 months before 65 means automatic enrollment.
Working past 65? (optional)
COBRA and retiree coverage do not count.
Whichever comes first.
Late sign-up check (optional)
See when coverage would start and any late penalty.
$/mo
$202.90 is the 2026 standard premium; edit for other years.
Enter your values to see the result.
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How to use the Medicare Enrollment Period Calculator
Enter your date of birth. The calculator finds the month Medicare considers you 65.
Tick the benefits box if you already receive Social Security or Railroad Retirement benefits.
If you have job-based coverage from current work, enter the date it or the job ends.
Optionally enter a planned Part B sign-up date to see when coverage starts and any late penalty.
Press Calculate enrollment dates and review the sign-up table and the list of enrollment periods.
How Medicare enrollment dates are calculated
Eligibility month: the month you turn 65. Under Social Security rules you reach an age the day before your birthday, so a birthday on the 1st puts your eligibility month one month earlier (born July 1 → June).
Initial Enrollment Period:IEP = first day of (eligibility month − 3) to last day of (eligibility month + 3).
Coverage start: sign up before the eligibility month → the 1st of the eligibility month; sign up in it or later in the IEP → the 1st of the next month.
Special Enrollment Period: while covered by a group plan from current work, plus the 8 months that begin the month after the job or coverage ends.
Part B penalty:10% × full 12-month periods without Part B after your IEP, counted to the end of the month you enroll.
Part D penalty:1% × national base beneficiary premium × months without creditable drug coverage (a gap of 63 days or more counts).
Example: turning 65 on June 15
Sign up in
Position in the IEP
Coverage starts
March
3 months before
June 1
April
2 months before
June 1
May
1 month before
June 1
June
Birthday month
July 1
July
1 month after
August 1
August
2 months after
September 1
September
3 months after
October 1
Yearly Medicare enrollment periods
Period
Dates
What you can do
General Enrollment Period
Jan 1 – Mar 31
Sign up for Part B or premium Part A if you missed your IEP
Medicare Advantage Open Enrollment
Jan 1 – Mar 31
Switch Medicare Advantage plans or return to Original Medicare
Annual Open Enrollment
Oct 15 – Dec 7
Join, switch or drop Medicare Advantage and Part D plans for Jan 1
Tips
Sign up in the 3 months before your birthday month to avoid any gap in coverage.
If you keep job coverage past 65, ask your employer for a written record of your coverage dates; Social Security asks for it when you enroll in Part B later.
Premium-free Part A (for most people with 40 quarters of work) has no late penalty, but contributing to an HSA must stop once Part A begins, and Part A can be backdated up to 6 months.
Premiums and penalty dollar amounts change every January; the Part B premium field defaults to the 2026 standard amount and can be edited.
This calculator applies the general Medicare rules published by Medicare.gov and the Social Security Administration. It is not affiliated with either agency; confirm your dates with SSA before you rely on them.
Frequently asked questions
When is my Medicare Initial Enrollment Period?
It is 7 months long: the 3 months before the month you turn 65, the month you turn 65, and the 3 months after. If you turn 65 in June, your IEP runs from March 1 to September 30. If your birthday is on the 1st of a month, Medicare treats you as turning 65 in the previous month, so the whole window starts one month earlier.
When does Medicare coverage start?
If you sign up in any of the 3 months before your birthday month, coverage starts on the first day of your birthday month. If you sign up in your birthday month or the 3 months after, coverage starts on the first day of the month after you sign up. These rules have applied since January 1, 2023.
Do I have to sign up for Medicare if I am still working?
Not always. If you or your spouse have group health coverage through current employment, you can usually delay Part B without a penalty and use a Special Enrollment Period later: you have 8 months after the job or coverage ends, whichever comes first. COBRA and retiree coverage do not count as current employment coverage. With fewer than 20 employees, Medicare may need to be primary, so check with the employer's plan.
How much is the Medicare Part B late enrollment penalty?
The penalty is 10% of the standard Part B premium for each full 12-month period you could have had Part B but did not, and it usually lasts as long as you have Part B. For example, signing up 26 months late means 2 full periods, so a 20% penalty. With the 2026 standard premium of $202.90, that is about $40.58 extra per month.
What is the General Enrollment Period?
If you missed your Initial Enrollment Period and do not qualify for a Special Enrollment Period, you can sign up for Part B (and premium Part A) from January 1 to March 31 each year. Coverage starts the first day of the month after you sign up, and a late penalty may apply.
Will I be enrolled in Medicare automatically?
Yes, if you already receive Social Security or Railroad Retirement Board benefits at least 4 months before you turn 65. You are enrolled in Part A and Part B starting the first day of the month you turn 65, and your card arrives about 3 months before your birthday. You can choose to decline Part B.
When is Medigap Open Enrollment?
Your Medigap Open Enrollment Period is the 6 months that start the first month you have Part B and are 65 or older. During it, insurers generally must sell you any Medigap policy they offer without medical underwriting. It does not repeat, so delaying Part B also delays this window.
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Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.