If you turn 65 in 2026, you have a seven-month window to sign up for Medicare without paying a lifetime late-enrollment penalty. Miss it without a qualifying exception, and the federal government adds 10% to your Part B premium for every full year you waited — and that surcharge follows you for as long as you have coverage.

The 2026 standard Part B premium is $202.90 a month, according to the Centers for Medicare & Medicaid Services. A two-year delay therefore costs you about $40.58 more every month, or roughly $487 a year. A three-year delay is $730 a year. Over a typical 20-year retirement, that adds up to thousands of dollars taken out of fixed-income budgets that mostly cannot absorb it.

The rules are not new, but two changes since 2023 — a faster coverage start date and tighter clarification of who qualifies for a Special Enrollment Period — have quietly reshaped the calendar. Here is what every American approaching 65 in 2026 needs to know.

The 7-month Initial Enrollment Period

The Initial Enrollment Period, or IEP, is the foundation of Medicare timing. It is a seven-month window built around the month you turn 65: the three months before your birthday month, the birthday month itself, and the three months after.

If you turn 65 in August 2026, your IEP runs from May 1 through November 30. Sign up in May, June, or July — the three months before — and your Medicare coverage starts the first day of your birthday month, August 1. Sign up in August, the birthday month itself, and coverage starts September 1. Sign up in the three months after, and coverage starts the first day of the month following enrollment — a meaningful improvement over the pre-2023 rules, when a delay inside the IEP pushed your start date out by an extra two or three months.

One technical exception trips people up every year: if your birthday falls on the first day of a month, the Social Security Administration treats you as having turned 65 the previous month. Your IEP shifts a month earlier — starting four months before your birthday month and ending two months after.

Most people do not need to do anything to enroll if they are already collecting Social Security at age 65. The SSA automatically signs them up for both Part A (hospital insurance) and Part B (medical insurance), and the Part B premium begins being withheld from the Social Security check. Everyone else — and that increasingly means most Americans, because the full retirement age for Social Security is now 67 and delayed claiming is the optimal move for many retirees — has to actively apply.

What happens if you miss the IEP: the General Enrollment Period

If you let the seven-month window close without enrolling and without a Special Enrollment Period (more on that below), the next chance to sign up is the General Enrollment Period (GEP) from January 1 to March 31 of each year.

The Consolidated Appropriations Act of 2021 changed how the GEP works in one important way, with the new rules taking effect January 1, 2023: before then, GEP coverage did not start until July 1, leaving a coverage gap that could stretch six months. Now, coverage begins the first day of the month after you enroll. Sign up in January, coverage starts February 1. Sign up in March, coverage starts April 1. The gap is gone — but the penalty is not.

The Part B late-enrollment penalty is permanent. It is calculated as 10% of the standard Part B premium for each full 12-month period you could have had Part B but did not. The math is unforgiving:

  • Two years late → 20% penalty → $40.58 a month extra → roughly $487 a year on top of the standard $202.90 Part B premium for 2026.
  • Three years late → 30% penalty → $60.87 a month → about $730 a year.
  • Five years late → 50% penalty → $101.45 a month → roughly $1,217 a year.

That surcharge does not stop when you finally enroll. It does not stop when you turn 70, 80, or 90. The federal government attaches it to your premium for as long as you have Part B — which, for most people, is the rest of their life.

Part D, the prescription drug benefit, carries a separate but parallel penalty. It is 1% of the “national base beneficiary premium” — $38.99 in 2026 — for each full month you went without creditable drug coverage after becoming eligible. That works out to roughly $0.39 a month per month of delay, rounded to the nearest 10 cents. Wait two full years to enroll in Part D in 2026 without other creditable coverage, and you owe an extra $9.40 a month on top of your plan premium — for life.

The 8-month Special Enrollment Period: a lifeline for workers past 65

Many Americans keep working past 65 and stay on their employer’s health plan. Medicare gives them an exception: a Special Enrollment Period (SEP) of up to 8 months that begins the month after their employer coverage or current employment ends — whichever comes first.

There is a critical trap here that catches thousands of new enrollees every year: COBRA continuation coverage and retiree health plans do not count as “current employment” for SEP purposes. If you retire at 67, take COBRA for 18 months, and then try to enroll in Medicare, your SEP clock started the month your active employment ended — not the month COBRA ran out. By the time you apply, the 8-month window may already have closed, leaving you stuck in the General Enrollment Period with a late penalty waiting.

The safer move for most people working past 65 is to enroll in Part A during the IEP — it is premium-free for the roughly 99% of beneficiaries with at least 40 quarters of Medicare-covered work — and then add Part B (and Part D) within the 8-month SEP after employment actually ends. Part A acts as a secondary payer alongside employer coverage and rarely creates a conflict, except for workers who contribute to a Health Savings Account, because enrolling in any part of Medicare ends HSA contribution eligibility going forward.

Where Medicare Advantage and Part D fit in the timeline

The Medicare Advantage and Part D enrollment calendars are layered on top of the Original Medicare timeline, not separate from it. To pick up Medicare Advantage (Part C) instead of Original Medicare, you first have to be enrolled in Parts A and B. You can do both at once during your IEP, or switch later.

The annual Medicare Open Enrollment Period runs October 15 through December 7 every year. That is when current beneficiaries can switch from Original Medicare to Advantage, switch between Advantage plans, change Part D plans, or move back to Original Medicare. Coverage from any change made during this window starts the following January 1. A second, narrower Medicare Advantage Open Enrollment Period runs January 1 through March 31, but only for people already enrolled in an Advantage plan who want to switch once or move back to Original Medicare.

How to actually sign up in 2026

For most people, enrollment in Original Medicare happens through the Social Security Administration, not through Medicare itself. The fastest route is the online application at ssa.gov/medicare/sign-up, which the SSA recommends starting about three months before the month you want coverage to begin. Applications can also be filed by phone (1-800-772-1213) or in person at a local SSA office by appointment.

The documents you will need are straightforward: proof of age (a birth certificate or passport), Social Security number, and — if you are still working — the dates of your employer’s health coverage so the SSA can certify your SEP eligibility correctly. If you are signing up after delaying because of employer coverage, you will also need Form CMS-L564, completed by your employer or your spouse’s employer, confirming that you had creditable group coverage for the entire period you delayed.

After enrollment, the red, white, and blue Medicare card arrives by mail. From there, the bigger questions begin: whether to stay with Original Medicare or move to a Medicare Advantage plan, which Part D plan best matches your prescriptions, and whether to buy a Medigap supplemental policy during the six-month Medigap Open Enrollment window that starts the month your Part B coverage begins. Those decisions are reversible to varying degrees. The decision about when to enroll in the first place is the one that locks in for life.

Three dates and three numbers to remember

For anyone turning 65 in 2026, the timeline simplifies to a small set of inputs. The three dates that matter are the three months before your birthday month (when you should ideally apply), the month you turn 65 (the standard coverage start point), and the three months after (the last on-time window inside the IEP). The three numbers are $202.90 (the 2026 Part B premium), $20.29 (the dollar value of every 10% late-enrollment penalty added monthly), and 8 months (the SEP window for workers past 65, beginning the month employment or employer coverage ends).

Medicare’s enrollment rules are forgiving in some respects — the coverage gap that haunted late enrollees before 2023 is gone, the SEP gives workers genuine flexibility, and the IEP itself is long enough to be hard to miss accidentally. But the late-enrollment penalty is exactly the kind of small, recurring tax that compounds quietly across two decades of retirement. Sign up on time, and the bill is just $202.90 a month. Miss the window, and the federal government quietly raises the price you pay every month for the rest of your life.

Sources: Centers for Medicare & Medicaid Services, “2026 Medicare Parts A & B Premiums and Deductibles” fact sheet (November 14, 2025); Medicare.gov, “When can I sign up for Medicare?” and “Avoid late enrollment penalties”; Social Security Administration, “When to sign up for Medicare”; CMS, “2026 Part D National Base Beneficiary Premium” (final 2026 figure $38.99); Consolidated Appropriations Act of 2021, Section 120 (coverage start-date reform, effective January 1, 2023).