You must sign up for Medicare at 65, but the exact important date depends on your work and insurance status

Most people must enroll in Medicare Part A (hospital insurance) and Part B (medical insurance) when they turn 65. However, if you are still working and covered by your employer's health plan, you may be able to delay Part B without penalty. The key is understanding your specific situation — because missing the important date when you should have signed up can cost you permanently higher premiums.

The Social Security Administration automatically enrolls you in Part A at 65 if you are already receiving Social Security benefits. If you are not yet receiving benefits, you will need to sign up yourself during your enrollment window. Part B is different: you must actively choose to enroll, and the timing matters.

Key Takeaways

  • You must enroll in Medicare Part A at 65 unless you are still working and covered by an active employer health plan.
  • Part B enrollment is your choice, but signing up late costs you 10 percent more per month for as long as you have Medicare — the penalty does not go away.
  • If you are covered by an employer plan when you turn 65, you can delay Part B without penalty as long as you enroll within eight months of losing that coverage.
  • Your enrollment window opens three months before your 65th birthday and closes three months after, giving you a seven-month window total.
  • You can sign up online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.

When you can delay enrollment without a penalty

If you are still working at 65 and your employer offers health insurance, you do not have to sign up for Part B right away. This is called having creditable coverage — insurance that is at least as good as Medicare Part B. Your employer's plan must cover at least as many services and have similar out-of-pocket costs.

The window to enroll without penalty is eight months after your coverage ends. So if you retire at 67 and lose your employer plan, you have until eight months after that date to sign up for Part B with no late-enrollment penalty. You must enroll during this window or face the 10 percent monthly premium increase.

Part A is different. If you are still working and have employer coverage, you can delay Part A enrollment as well — but only if your employer has 20 or more employees. If your employer is smaller, you must enroll in Part A at 65 even if you are still working.

What happens if you miss the important date

If you do not enroll in Part B when you should have, Medicare charges you a late-enrollment penalty of 10 percent of the standard Part B premium for each full year you were may be able to access but not enrolled. This penalty is permanent — it stays on your premium for the rest of your life, even if you enroll years later.

For example, if the standard Part B premium is $165 per month and you delay enrollment by three years without a valid reason, your premium becomes $165 plus 10 percent for each year, which is $49.50 extra per month. That extra $49.50 stays with you forever.

The only way to avoid this penalty is to enroll during your initial enrollment window (three months before to three months after your 65th birthday) or to have creditable coverage from an employer plan. If you have creditable coverage, keep written proof — your employer's plan documents or a letter from your benefits department stating that your coverage meets Medicare standards.

How to sign up for Medicare

You can enroll in Medicare three ways: online, by phone, or in person. The online option is the fastest. Go to Medicare.gov and click "Sign Up for Medicare" to create an account and complete your enrollment. You will need your Social Security number and information about any current health coverage.

If you prefer to speak with someone, call 1-800-MEDICARE (1-800-633-4227). Representatives are available Monday through Friday, 8 a.m. to 8 p.m. Eastern time. They can walk you through the process and answer questions about your specific situation.

You can also visit your local Social Security office in person. Find the office nearest you at ssa.gov/locator. Bring your Social Security card, proof of citizenship or legal residency, and proof of age (birth certificate or passport).

If you are still working past 65

Working past 65 does not automatically mean you can skip Medicare. You must still enroll in Part A at 65 if your employer has fewer than 20 employees. If your employer has 20 or more employees, you can delay both Part A and Part B as long as you have employer coverage.

When you do retire and lose your employer plan, you have a special enrollment period of eight months to sign up for Part B without penalty. This is your safety net — use it. If you miss this window, the 10 percent penalty applies.

Some people worry that enrolling in Medicare while still working will affect their job or benefits. It will not. Medicare and your employer plan can work together, with Medicare paying second after your employer plan.

Special situations: disability and end-stage renal disease

If you receive Social Security Disability Insurance (SSDI), you become may be able to access for Medicare automatically after you have been on disability for 24 months. You do not have to wait until 65. Medicare will enroll you in both Part A and Part B unless you decline Part B in writing.

If you have end-stage renal disease (ESRD) and need dialysis or a kidney transplant, you may be may be able to access for Medicare regardless of age. Contact your dialysis center or transplant team to learn about your enrollment options.

Frequently Asked Questions

What if I do not want Medicare Part B?

You can decline Part B in writing when you turn 65, but only if you have creditable coverage from an employer plan. If you decline without creditable coverage, you will face a late-enrollment penalty when you eventually sign up. Keep your written declination letter for your records.

Can I change my mind after I enroll?

Yes, during the General Enrollment Period, which runs January 1 through March 31 each year. Changes take effect July 1. However, if you are making changes because you missed your initial important date, a late-enrollment penalty may still explore.

Do I have to enroll in Part D (prescription drug coverage) at 65?

Part D is optional, but if you do not enroll when you are first may be able to access and later sign up, you will pay a late-enrollment penalty on your premiums. If you do not take prescription drugs, you can decline Part D, but enroll as soon as you need it to avoid the penalty.

What if I am not a U.S. citizen?

You must be a U.S. citizen or a permanent resident who has lived in the United States for at least five years to enroll in Medicare. If you meet these requirements, you can enroll at 65 just like any other person. Bring proof of legal residency when you sign up.

Can my spouse sign up for Medicare before 65?

No. Medicare may be able to access begins at 65 for most people, regardless of your spouse's age or status. The only exceptions are people on SSDI (after 24 months) or those with ESRD. Your spouse must wait until their 65th birthday to enroll.