You should sign up for Medicare Part A during your initial enrollment period, which starts three months before the month you turn 65

Your initial enrollment period lasts seven months total: three months before you turn 65, the month you turn 65, and three months after. If you sign up during this window, your Part A coverage begins on the first day of the month you turn 65. If you miss this period, you can still sign up later, but you may face a permanent penalty on your premiums and a gap in coverage.

Most people do not pay a premium for Part A if they or their spouse paid Medicare taxes for at least 10 years while working. If you do not meet this requirement, you can still get Part A, but you will pay a monthly premium. The amount depends on how many years you or your spouse worked and paid into Medicare.

The important date matters because waiting beyond your initial enrollment period can cost you money for the rest of your life. A late enrollment penalty adds 10 percent to your Part A premium for twice the number of months you delayed — so waiting two years means paying 40 percent more, permanently.

Key Takeaways

  • Your initial enrollment period runs from three months before you turn 65 through three months after, and signing up during this time means coverage starts on your 65th birthday.
  • Most people pay no premium for Part A if they worked and paid Medicare taxes for at least 10 years, but you must still sign up to receive coverage.
  • Missing your initial enrollment period triggers a permanent penalty of 10 percent per year of delay, added to your Part A premium for life.
  • You can sign up through Social Security, Medicare.gov, or by calling 1-800-MEDICARE, and the process takes about 15 minutes.
  • If you are still working at 65 and have health insurance through your job, you may be able to delay Part A without penalty under specific circumstances.

The seven-month window: when your initial enrollment period opens and closes

Social Security automatically sends you information about Medicare three months before your 65th birthday. This is when your initial enrollment period officially begins. You have until the end of the third month after your birthday to sign up without facing a late penalty.

The exact dates depend on your birth month. If you were born on June 15, your initial enrollment period runs from March 1 through September 30. If you were born on June 1, it runs from March 1 through August 31. The month of your birthday is always included in the middle of the window.

Signing up early in this period gives you time to resolve any problems before coverage starts. Many people sign up in the month they turn 65 or the month before, which leaves a buffer if documents need to be verified or if questions arise.

What happens if you miss your initial enrollment period

If you do not sign up during your initial enrollment period, you enter what Medicare calls a general enrollment period. This runs from January 1 through March 31 each year, and you can sign up then. However, your coverage will not start until July 1 of that year — meaning you could have a gap of several months with no Part A coverage.

More importantly, you will owe a late enrollment penalty. This penalty is 10 percent of the standard Part A premium for each full 12 months you were may be able to access but did not sign up. If you waited two years, you pay 20 percent more. If you waited five years, you pay 50 percent more. This penalty stays on your bill for as long as you have Part A.

The only exception is if you had creditable coverage — health insurance through an employer or union that was at least as good as Medicare Part A — during the months you delayed. If you can prove you had that coverage, you may not owe a penalty. You will need to provide documentation from your former employer or insurance company.

Special cases: when you can delay Part A without penalty

If you are still working at 65 and your employer has 20 or more employees, you may be covered under your employer's group health plan instead of Medicare. In this case, you can delay Part A without penalty as long as you are actively employed and covered by that plan. Once you leave that job or lose the coverage, you have eight months to sign up for Part A without owing a penalty.

If your employer has fewer than 20 employees, Medicare becomes your primary insurance at 65, and you should sign up during your initial enrollment period even if you are still working. Delaying in this situation will trigger a penalty.

If you are receiving Social Security benefits before age 65, you are automatically enrolled in Part A and Part B at 65 unless you specifically decline Part B. You do not need to take any action for Part A in this case.

How to sign up for Part A during your enrollment period

You have three main ways to sign up. The easiest is online at Medicare.gov — go to the "Sign Up" section and follow the steps. You will need your Social Security number, birth date, and citizenship information. The process takes about 15 minutes.

You can also call 1-800-MEDICARE (1-800-633-4227) and speak to a representative. They can answer questions while you sign up and can often complete your enrollment over the phone. The line is open Monday through Friday, 8 a.m. to 8 p.m. Eastern time.

A third option is to visit your local Social Security office in person. Bring your Social Security card, proof of citizenship (passport, birth certificate, or naturalization papers), and proof of residency (utility bill or lease). Staff can help you sign up and answer questions about your specific situation.

What Part A covers and why timing matters

Part A covers inpatient hospital stays, skilled nursing facility care, hospice care, and some home health services. It does not cover outpatient doctor visits, prescription drugs, or routine care — those are covered by Part B and other parts of Medicare. Part A is the foundation of Medicare coverage, which is why signing up on time is important.

If you delay Part A and end up in the hospital before you sign up, Medicare will not pay for that stay. You will be responsible for the full bill. This is one of the biggest financial risks of missing your enrollment period. Even a short hospital stay can cost tens of thousands of dollars.

Frequently Asked Questions

What if I turn 65 and I am still working full-time?

If your employer has 20 or more employees and you are covered by their health plan, you can delay Part A without penalty. Once you stop working or lose that coverage, you have eight months to sign up. If your employer has fewer than 20 employees, you should sign up for Part A during your initial enrollment period, even though you are working.

Can I sign up for Part A after my initial enrollment period ends?

Yes, you can sign up during the general enrollment period from January 1 through March 31 each year, and coverage starts July 1. However, you will owe a late enrollment penalty of 10 percent per year of delay, and this penalty is permanent. The only exception is if you had creditable coverage through an employer during the months you delayed.

Do I have to pay a premium for Part A?

Most people pay no premium for Part A if they or their spouse worked and paid Medicare taxes for at least 10 years. If you do not meet this requirement, you will pay a monthly premium. The exact amount varies, but it is typically between $278 and $505 per month in 2024, depending on your work history.

What if I am receiving Social Security before 65?

You are automatically enrolled in Part A and Part B at age 65 unless you specifically decline Part B. You do not need to take any action to sign up for Part A. You will receive your Medicare card in the mail about two weeks before your 65th birthday.

Can I decline Part A if I have other insurance?

You can decline Part B if you have creditable coverage through an employer, but declining Part A is not recommended and is rarely necessary. Part A has no premium for most people, so there is little reason to turn it down. If you have questions about your specific situation, call 1-800-MEDICARE to discuss your options.