Turning 65: what to actually do, and when

The short answer: your Initial Enrollment Period is seven months long — the three months before your birthday month, your birthday month, and the three months after. If you want coverage to start the day you turn 65, act in those first three months. If you are still working and covered by a large employer's plan, you may be able to wait without a penalty — but that depends on the size of the employer, so check before you assume.

That is the whole thing in a paragraph. The rest of this page is what sits underneath it.

When exactly does my enrollment window open?

Three months before the month you turn 65, and it runs for seven months total.

So if your birthday is in September, your Initial Enrollment Period — what this means runs June through December. June, July and August are the "before" months. September is your birthday month. October, November and December are the "after" months.

What if I am still working at 65?

Then it depends on how big the employer is, and this is the question people most often get wrong by guessing.

If you are covered by a group health plan through current employment at an employer with 20 or more employees, you can usually delay Part B without a late penalty and pick it up later through a Special Enrollment Period. If the employer has fewer than 20 employees, Medicare generally pays first, and delaying can leave you badly exposed.

Retiree coverage and COBRA are not the same as current employment coverage for this purpose. That distinction catches people every year.

If any of this describes you, read the longer version for people still working at 65 before you make a decision.

What happens if I miss it?

Two penalties, and both are permanent for as long as you hold the coverage.

Part B: the premium increases by 10% for each full 12-month period you could have had Part B and did not. You pay that increase for as long as you have Part B.

Part D: the penalty is calculated per month you went without creditable drug coverage and is added to your premium for as long as you have Part D. "I do not take any prescriptions" is the most common reason people skip Part D, and it is the most expensive one, because the penalty is based on how long you waited, not on what you needed.

What should I do next?

1. Find your seven-month window. Count back three months from your birthday month.
2. Work out whether you are delaying Part B on purpose. If you are still working, confirm the employer size and whether the coverage counts as current employment.
3. Write down your doctors and your prescriptions before you compare anything. Every route depends on that list.
4. Decide the Original Medicare vs Medicare Advantage question knowingly, not by default — Medicare Advantage or Medigap, compared honestly.
5. Check your enrollment window with the two-minute eligibility check.

If you are in northern New Jersey, Bergen County works a little differently than you might expect, because plan availability is set county by county. There are equivalent notes for New York City and Philadelphia.

Where these rules come from

Enrollment periods, penalties and Medigap rights are federal rules. They change rarely, but they do change, and the amounts attached to them are set annually. Check the current figures against the official sources rather than any advisor's page, including this one:

• Medicare.gov — when to sign up
• Medicare.gov — Part B late enrollment penalty
• Medicare.gov — Part D late enrollment penalty
• Medicare.gov — when can I buy Medigap?

Last reviewed: 28 July 2026. This page explains how the rules work. It does not list premiums, deductibles or plans, because those are set each year and vary by county — which is exactly the sort of thing worth confirming for your own situation before you decide anything.