Key takeaways
  • Your Initial Enrollment Period runs 3 months before to 3 months after your 65th-birthday month — enroll in the first 3 months for the earliest start date.
  • Join a Part D drug plan during this window or keep creditable drug coverage to avoid a permanent late penalty.
  • Still working? You may be able to delay Part B and Part D penalty-free with qualifying employer coverage.

Turning 65 in 2027? Your Medicare clock starts earlier than most people expect. Miss your enrollment window and you can face gaps in coverage — plus a permanent Part D late-enrollment penalty. Here is the timeline, month by month.

Your 7-month Initial Enrollment Period

Your Initial Enrollment Period (IEP) is a fixed seven-month window around your 65th birthday: the three months before your birthday month, your birthday month, and the three months after.

For example, if your 65th birthday is in July 2027, your IEP runs from April 1, 2027 through October 31, 2027. You cannot move or extend this window, and it only happens once — it is the easiest and cheapest time to get into Medicare.

One quirk worth knowing: if your birthday falls on the 1st of the month, Medicare treats you as turning 65 the month before, so your seven-month window shifts one month earlier.

Already receiving Social Security benefits? If you applied for Social Security or Railroad Retirement benefits more than four months before turning 65, you may be automatically enrolled in Part A and Part B, with your Medicare card arriving by mail. Everyone else must take action.

When your coverage actually starts

The month you sign up within your IEP determines when coverage begins:

Enroll in the three months before your birthday month: Part A and Part B start on the first day of your birthday month. Enroll during your birthday month or the three months after: coverage starts on the first day of the month after you sign up.

That is why the first three months are the sweet spot — enrolling early gives you seamless coverage starting the month you turn 65, with no gap. Wait until month five or six, and you could be uninsured for weeks while the start date catches up.

Part D: pick your drug plan during this window

Medicare Part D prescription drug coverage does not come automatically — you choose a stand-alone Part D plan (PDP) or a Medicare Advantage plan with drug coverage (MA-PD) through a private insurer. Your IEP is the time to do it.

If you skip drug coverage and go 63 days or more without Part D or other creditable drug coverage (drug coverage expected to pay at least as much as standard Part D, such as most employer plans, VA benefits, or TRICARE), you owe a late-enrollment penalty — a permanent monthly surcharge added to your Part D premium.

How it works: the penalty equals 1% of the national base beneficiary premium for each full month you went without creditable coverage, rounded to the nearest 10 cents. For 2026 that base premium was $38.99, so a 12-month gap adds roughly $4.70 per month — and it stays on your bill for as long as you have drug coverage, recalculated each year as the base premium changes. Enrolling in Part D on time costs you nothing extra; waiting has a lifetime price tag.

Still working past 65? Special rules apply

Not everyone needs to enroll at 65. If you (or your spouse) still work for an employer and have group health coverage from current employment, you can generally delay Part B — and Part D — without penalty, then enroll later through a Special Enrollment Period (an 8-month SEP once the job or coverage ends).

Two catches to know:

  1. Creditable drug coverage is the key. Your employer plan must count as creditable prescription drug coverage to avoid the Part D penalty. Your employer or plan must notify you in writing each year whether your coverage is creditable — keep that letter as proof.
  2. HSA warning. Contributing to a Health Savings Account stops being allowed once you enroll in Medicare (including premium-free Part A). If you plan to keep funding an HSA past 65, do not take Part A early.

COBRA and retiree coverage do not count as current employment — they don't let you delay without penalty.

What to have ready before you apply

Most people enroll through Social Security — online at ssa.gov, by phone at 1-800-772-1213, or in person. Gather these ahead of time:

  1. Your Social Security number and a government-issued ID (driver's license or passport).
  2. Your birth certificate or other proof of age.
  3. Proof of U.S. citizenship or legal residency.
  4. If delaying: a letter from your employer confirming your group coverage is creditable.
  5. A list of your current prescriptions — so you can compare Part D plan formularies before you choose.

Start comparing drug plans 4–6 months before your birthday month. Every plan's formulary, tier structure, and pharmacy network differ, and the cheapest premium is rarely the whole story.

If you miss the window

Miss your IEP without qualifying coverage and you generally wait for the General Enrollment Period (January 1 – March 31) each year, with coverage starting the month after you enroll — plus the Part D and Part B late penalties described above. A short gap in the right part of your IEP is fixable; missing it entirely can cost you coverage and money for months.

Bottom line: Your seven-month window around your 65th birthday is the single cheapest, simplest time to set up Part D — enroll in the first three months for seamless coverage, keep proof of creditable coverage if you delay, and compare plan formularies before you pick.