When Do I Actually Sign Up for Medicare?

Do I have to sign up when I turn 65?

This is the question people actually type into the search bar, so let's take it head on. Medicare isn't mandatory. No one is required to sign up at 65, and there's no fine for skipping it. What the rules do instead is make waiting expensive: if you delay Part B (Medical Insurance, the part that covers doctors and outpatient care) without coverage that qualifies you for an exception, you can face a gap with no coverage and a monthly penalty that lasts as long as you have Part B. So the honest answer is "no, but for most people without other coverage, waiting costs real money." Source: Medicare.gov, 2026.

One group doesn't have to do anything at all. If you started Social Security benefits at least 4 months before you turn 65, you're enrolled in Part A (Hospital Insurance) and Part B automatically, and a welcome package with your Medicare card arrives in the mail about 3 months before coverage starts. Everyone else signs themselves up. Source: Medicare.gov and SSA, 2026.

How does the 7-month window work?

The official name is the Initial Enrollment Period, but "the 7-month window" tells you everything you need. When you sign up inside the window changes when coverage begins, and coverage always starts on the first of a month:

• Months 1 to 3 The three months before your birthday month. Sign up here and coverage starts the first day of the month you turn 65. This is the timing most people want.
• Month 4 Your birthday month. Sign up now and coverage starts the first day of the next month.
• Months 5 to 7 The three months after your birthday month. Coverage starts the first day of the month after you sign up.

Source: Medicare.gov, "When does Medicare coverage start?", 2026.

So if you turn 65 on May 11, your window runs February 1 through August 31, and signing up in February, March, or April gets you covered on May 1. If you're helping a parent with this, that's the whole calculation: find the birthday month, count three months back, count three months forward. Source: RRB.gov enrollment examples, 2026.

What if my birthday is on the first of the month?

Here's the quirk. If your birthday falls on the first day of a month, Medicare treats you as if you turned 65 the month before, and your whole 7-month window shifts one month earlier. Turn 65 on May 1 and your window runs January 1 through July 31, not February through August. Your coverage can also start a month earlier than a May 11 birthday would allow. It only applies to birthdays on the 1st. Born on the 2nd or later, even the 2nd itself, and the normal window applies. Source: CMS, Medicare & You 2026; RRB.gov, 2026.

What happens if I miss my window?

Two things, and neither is the end of the world, but both are worth avoiding.

First, you wait. If you miss the 7-month window and don't qualify for an exception, your next chance is the General Enrollment Period, which runs January 1 through March 31 every year. Coverage starts the first of the month after you sign up. Depending on when your window closed, that can mean months without coverage. Source: Medicare.gov, 2026.

Second, the Part B late penalty. Your monthly Part B premium goes up 10% for each full 12-month period you could have had Part B but didn't sign up, and you keep paying that higher premium for as long as you have Part B. For most people that means for life. In 2026 the standard Part B premium is $202.90 a month, so someone who signed up two full years late would pay a 20% penalty on top of it, about $243.50 a month at 2026 rates. The percentage sticks even as the base premium changes each year. Source: Medicare.gov, "Avoid late enrollment penalties," 2026.

Part A is a gentler story. Most people get Part A without a monthly premium because they (or a spouse) paid Medicare taxes long enough, and premium-free Part A has no late penalty. Only people who have to buy Part A can owe a Part A penalty, and that one does eventually end. Source: Medicare.gov, 2026.

What if I'm still working at 65?

This is the exception the penalty warnings always skip, and it's the reason so many people ask "I'm still working, do I have to sign up?" If you're 65 and covered by health insurance from your own current job or your spouse's current job, you generally don't need Part B yet and you won't owe a penalty for waiting. You get a Special Enrollment Period instead: you can sign up any time while that job-based coverage lasts, and for 8 months after the job or the coverage ends, whichever comes first. Many people in this spot still take premium-free Part A at 65 and simply wait on Part B, with one important exception: if you contribute to a Health Savings Account (HSA), those contributions have to stop once Part A starts, and Part A can even be backdated, which is another reason to read the still-working guide before you sign up for anything. Source: Medicare.gov and SSA, 2026.

The details matter here, including employer size and what happens with COBRA, so we've put the whole situation in its own guide: Still working at 65? Read this before you sign up.

Quick answers to the questions people actually ask

Is the big fall enrollment period my sign-up window?

No, and this trips up a lot of families. The fall window you see advertised everywhere is for people who already have Medicare to change their coverage. Your first sign-up uses the 7-month window on this page. Once you're in, our AEP (Annual Enrollment Period) game plan covers what the fall window is actually for.

Where do I actually sign up?

Through Social Security, even though the coverage is Medicare. You can apply online at SSA.gov, call Social Security, or visit a local office. If you're already getting Social Security benefits, check the mail instead: you may be enrolled automatically.

Do I have to take Part B if I have other coverage?

It depends on what the other coverage is. Job-based insurance from current employment usually lets you delay Part B safely; retiree coverage and COBRA usually don't. When it's not obvious, a free SHIP counselor can look at your exact situation, and the links below don't sell anything.

How do I figure out my mom's or dad's window?

Take their birthday month, count three months before and three months after. That's the window. If the birthday is on the 1st of a month, slide the whole thing one month earlier. Signing up in the three months before the birthday month gives them the smoothest start.