Medicare enrollment happens through Social Security, Medicare.gov, or your local Social Security office — and the timing matters because late enrollment can cost you

You enroll in Medicare through Social Security, either online at Medicare.gov, by phone at 1-800-MEDICARE (1-800-633-4227), or in person at your local Social Security office. If you are already receiving Social Security benefits when you turn 65, Medicare Part A and Part B are usually enrolled automatically three months before your 65th birthday. If you are not yet receiving Social Security, you must enroll yourself during your Initial Enrollment Period — the seven-calendar-month window that begins three months before the month you turn 65 and ends three months after.

The enrollment method you choose does not change your coverage or cost. Online enrollment through Medicare.gov is fastest if you have a Social Security account set up. Phone enrollment takes longer but does not require internet access. In-person enrollment at a Social Security office is useful if you have documents to show or questions that need real-time answers.

Key Takeaways

  • If you receive Social Security, Medicare Part A and Part B enroll automatically three months before you turn 65; you do not need to do anything.
  • If you do not receive Social Security, you must enroll during your Initial Enrollment Period — a seven-month window centered on your 65th birthday — or face permanent late-enrollment penalties.
  • You can enroll online at Medicare.gov, by phone at 1-800-MEDICARE, or at your local Social Security office; all three routes lead to the same coverage.
  • Part A (hospital insurance) is usually free at 65 if you or your spouse paid Medicare taxes for at least 10 years; Part B (medical insurance) has a monthly premium that increases if you delay.
  • If you are still working at 65 and have health insurance through your job, you may be able to delay Part B without penalty, but you must report this to Medicare.

Automatic enrollment if you already receive Social Security

If you are receiving Social Security retirement, disability (SSDI), or Railroad Retirement Board benefits when you turn 65, Social Security automatically enrolls you in Medicare Part A and Part B. You will receive a Medicare card in the mail about two weeks before your coverage starts — usually the first day of the month you turn 65. You do not need to do anything, and you do not need to contact anyone.

Check the card when it arrives to make sure your name, date of birth, and Social Security number are correct. If anything is wrong, call 1-800-MEDICARE to report it. If you do not receive your card by the expected date, call the same number to request a replacement.

Manual enrollment if you do not receive Social Security

If you are not receiving Social Security benefits at 65, you must enroll in Medicare yourself during your Initial Enrollment Period. This seven-month window opens three months before the month you turn 65 and closes three months after. For example, if you turn 65 in June, your enrollment period runs from March through September.

You can enroll online, by phone, or in person. Online enrollment at Medicare.gov is the fastest route if you have a Social Security account; you can complete it in about 10 minutes. Phone enrollment at 1-800-MEDICARE takes 15 to 20 minutes and does not require internet access. In-person enrollment at your local Social Security office is useful if you have questions or need to show documents like your birth certificate or proof of citizenship.

Enroll as early in your Initial Enrollment Period as you can. If you wait until the last month, processing delays may mean your coverage does not start on time, and you could face a gap in protection.

What happens if you miss your Initial Enrollment Period

If you do not enroll during your Initial Enrollment Period and you are not still working with employer health insurance, you will face a late-enrollment penalty on Part B that lasts for the rest of your life. The penalty is 10 percent of the Part B premium for each full 12 months you were may be able to access but not enrolled. If the standard Part B premium is $165 per month and you were late by three years, your penalty would be 30 percent of that premium, added to your monthly bill permanently.

Part A also has a late-enrollment penalty if you do not have it based on work history, but Part A penalties are less common because most people at 65 are covered through their own or a spouse's work record.

There is one exception: if you were still working at 65 and had health insurance through your employer, you may be able to delay Part B without penalty. You must report this to Medicare using Form CMS-L564 (Employer Group Health Plan Certification) so that Medicare knows you had creditable coverage. Without this form on file, Medicare will assume you were uninsured and will assess the penalty.

Enrolling in Part D (prescription drug coverage) at the same time

When you enroll in Part A and Part B, you can also enroll in a Part D plan (prescription drug coverage) during the same Initial Enrollment Period. Part D enrollment is separate from Part A and B — you choose a specific plan from a list of insurers in your area, and the plan you pick affects your monthly cost and which pharmacies you can use.

If you do not enroll in Part D when you first become may be able to access and you go without creditable drug coverage for more than 63 days, you will also face a late-enrollment penalty on Part D. This penalty is 1 percent of the national average Part D premium for each month you were late, and it also lasts for the rest of your life.

You can enroll in Part D at the same time you enroll in Part A and B through Medicare.gov, by phone, or in person. The enrollment process asks you to choose a plan; if you are unsure which plan covers your medications at the lowest cost, Medicare.gov has a plan-comparison tool that shows you options based on your prescriptions and preferred pharmacies.

Enrolling in a Medicare Advantage plan instead of Original Medicare

Instead of Original Medicare (Part A and B), you can choose a Medicare Advantage plan (also called Part C) during your Initial Enrollment Period. Medicare Advantage plans are offered by private insurers and usually include prescription drug coverage, dental, vision, and hearing benefits that Original Medicare does not cover. However, they typically have smaller networks of doctors and hospitals, and they require you to use in-network providers except in emergencies.

If you choose a Medicare Advantage plan, you still enroll through Medicare.gov, by phone, or in person — the process is the same as for Original Medicare. You pick the specific plan you want, and your coverage starts on the first day of the month after Medicare receives your enrollment.

You can switch from Original Medicare to Medicare Advantage, or from Medicare Advantage back to Original Medicare, during the Annual Enrollment Period (October 15 through December 7 each year). Changes made during this window take effect January 1 of the following year.

Documents and information you will need

To enroll in Medicare, have the following ready: your Social Security number, your date of birth, your citizenship or immigration status, and information about any current health insurance you have (such as an employer plan or COBRA coverage). If you are enrolling in person, bring your original birth certificate or passport, proof of citizenship (such as a naturalization certificate), and proof of residency (such as a utility bill or lease).

If you are enrolling online, you will not need to show documents at the time of enrollment, but Medicare may contact you later to verify information. If you are enrolling by phone, have your documents nearby in case the representative asks you to confirm details.

Frequently Asked Questions

Do I have to enroll in Medicare at 65 if I am still working?

You do not have to enroll in Part B if you have health insurance through your current employer and are actively working. However, you should still enroll in Part A (hospital insurance) because it is usually free and has no monthly premium. To avoid a Part B late-enrollment penalty later, report your employer coverage to Medicare using Form CMS-L564 so the agency knows you had creditable coverage.

What if I turn 65 in a month with fewer than 31 days?

Your Initial Enrollment Period is still seven months long and is centered on the month you turn 65. For example, if you turn 65 in February, your enrollment period runs from November of the previous year through May. The number of days in the month does not change the window.

Can I enroll in Medicare before I turn 65?

You can enroll starting three months before the month you turn 65. For example, if you turn 65 in September, you can enroll starting June 1. Enrolling early is a good idea because it gives Medicare time to process your enrollment and mail your card before your coverage starts.

What if I miss the important date to enroll in Part D?

If you miss your Initial Enrollment Period for Part D, you can enroll during the Annual Enrollment Period (October 15 through December 7) each year, but you will face a late-enrollment penalty if you go without creditable drug coverage for more than 63 days. The penalty is permanent and is calculated as 1 percent of the national average Part D premium for each month you were late.

How long does it take to get my Medicare card after I enroll?

If you enroll online or by phone, Medicare usually mails your card within two to three weeks. If you enroll in person at a Social Security office, the timeline is the same. Your coverage starts on the date Medicare approves your enrollment, even if your card has not arrived yet. If you do not receive your card within three weeks, call 1-800-MEDICARE to request a replacement.