Turning 65: The 7-Month Medicare Enrollment Checklist and Deadlines

When does your Initial Enrollment Period start and end?

Medicare calls your first sign-up window 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. Nothing about the date on your birth certificate matters except the month it falls in.

Take a June 12 birthday. Your enrollment period will extend from March 1 through September 30. Coverage always starts on the first of the month, so the month you file the application, not the day, sets your start date. Medicare answers birthdays that fall on the first of the month separately, and those windows shift one month earlier.

That table is the whole argument for acting early. Filing in month one of seven gives you coverage on the first day of your birthday month. Filing in month five can push your start date into month six.

What should you do three months before your birthday month?

Three tasks, and none of them take long. First, find out whether you will be enrolled automatically or need to apply. If you are already receiving Social Security benefits when you turn 65, you will automatically be enrolled in Part A and Part B. If you are not drawing benefits yet, you apply through Social Security yourself.

Second, get your employer situation in writing. Social Security says if you or your spouse have health insurance through your job, you can sign up any time while working and still covered by the group health plan. Ask your benefits administrator for the employee count and for a creditable drug coverage notice, and keep both.

Third, write down your doctors, hospitals, and prescriptions before anyone shows you a plan. That list decides whether Original Medicare with a supplement or a Medicare Advantage plan fits your year better, and our side-by-side look at Medicare Advantage and Medigap for 2027 walks through the trade-offs. You can also start from our Medicare resource hub.

Do you need both Part A and Part B on day one?

Usually yes. Most people sign up for both Part A and Part B when they are first eligible, there are generally risks to signing up later such as a gap in coverage or a penalty, though in some cases it might make sense to sign up later. The main exception is active employer coverage, covered in the next section.

Part A has more flexibility than Part B. You can sign up for Part A any time after you turn 65, your Part A coverage starts 6 months back from when you sign up or when you apply for Social Security benefits, and coverage cannot start earlier than the month you turned 65. That retroactive start is exactly why health savings accounts get complicated. Social Security notes that contributing to an HSA after your Medicare coverage begins may result in additional taxes. Confirm the contribution cutoff with your CPA before you file.

What does a late sign-up actually cost?

Medicare publishes the arithmetic. If you waited 2 full years, 24 months, to sign up for Part B and did not qualify for a Special Enrollment Period, you will pay a 20 percent late enrollment penalty, 10 percent for each full 12-month period that you could have signed up, plus the standard Part B monthly premium of $202.90 in 2026. That works out to a $243.50 Part B monthly premium for 2026, rounded to the nearest 10 cents and including the penalty. The surcharge is not temporary: you may pay a monthly late enrollment penalty for as long as you have Part B coverage. The 2027 standard premium had not been published when we verified this post, so check medicare.gov for the current-year figure.

Drug coverage has a separate clock. You may owe a penalty if at any time after your Initial Enrollment Period is over there is a period of 63 or more days in a row when you do not have Medicare drug coverage or other creditable prescription drug coverage. The penalty is 1 percent times the national base beneficiary premium times the number of full uncovered months, rounded to the nearest 10 cents and added to your monthly premium. CMS set that benchmark for next year: for 2027, the base beneficiary premium will be $41.33. Twelve uncovered months would add roughly $5 a month, permanently. Our Part D hub and our breakdown of the 2027 Part D deductible and out-of-pocket cap cover what the plans themselves look like next year.

What if you are still working at 65?

Active group coverage can delay Part B without a penalty. CMS says that with this Special Enrollment Period, a person can sign up for Part B without a penalty anytime while they are covered by the employer or union group health plan based on current employment, or up to 8 months after the group health plan coverage or the employment ends, whichever happens first.

Two details decide whether that protection is real for you. Employer size drives coordination: if a person is eligible for Medicare due to age, their employer-based insurance from current employment will pay first if the employer has more than 20 employees, and if Medicare pays first and a person is not enrolled in Part B, the other insurance may not pay all the uncovered costs. And the coverage must be current employment coverage, because COBRA and retiree health plans do not count, and people with that coverage are not eligible for a Special Enrollment Period when it ends.

If you work for a company with fewer than 20 employees, treat your Initial Enrollment Period as the real deadline. Ask your employer to confirm the count in writing, then keep the letter with your Medicare card.

When do you choose Medigap, Medicare Advantage, or Part D?

After Part B is effective, and often in the same conversation. The supplement window is the one people lose without noticing: under federal law you get a 6 month Medigap Open Enrollment Period, starting the first month you have Medicare Part B and you are 65 or older. During it, an insurance company cannot refuse to sell you any of the medical policies it offers and cannot use medical underwriting to decide whether to accept your application. After that period, your options to buy a Medigap policy may be limited and the policy may cost more. Guaranteed-issue rights and underwriting rules after the window vary by state, so ask before you assume. Our plain-English introduction to Medicare Supplement plans explains how the lettered plans line up.

If you turn 65 in October, November, or December, you are working two calendars at once. Your Initial Enrollment Period handles Part A and Part B, and the Annual Enrollment Period of October 15 to December 7 handles drug and Medicare Advantage choices for January 1. Our post on what the Annual Enrollment Period does and does not let you change keeps those two windows straight.

Which dates belong on your calendar?

Copy these into your phone with the actual months filled in. Month one is three months before your birthday month, and month seven is three months after it.

One last note on timing. After your Initial Enrollment Period ends, you can only sign up for Part B and premium-Part A during one of the other enrollment periods, and those periods come with waiting and, in many cases, a lifelong surcharge. Starting the paperwork in month one costs you nothing and removes that risk entirely.