Your Medicare coverage begins on the first day of the month you turn 65, or the first day of the month you become may be able to access due to disability or end-stage renal disease

If you turn 65 on any day of the month, your Part A (hospital insurance) and Part B (medical insurance) coverage starts on the first of that month — not on your birthday itself. For example, if you turn 65 on March 15, your coverage begins March 1. If you turn 65 on April 1, your coverage still begins April 1.

If you become may be able to access before 65 because of a disability information or end-stage renal disease, the same rule applies: coverage begins on the first day of the month you meet the medical criteria, not the day you receive notice.

The timing matters because it affects when you pay your first premium and when you can use your benefits. Understanding your start date helps you plan for costs and avoid gaps in coverage.

Key Takeaways

  • Medicare Part A and Part B coverage begins on the first day of the month you turn 65, regardless of which day of the month your birthday falls on.
  • If you sign up during your Initial Enrollment Period (the seven-month window around your 65th birthday), your coverage will start on the first of the month you turn 65 with no waiting period.
  • If you miss your Initial Enrollment Period and sign up late, your Part B coverage may not start until months later, and you may owe a permanent penalty on your premiums.
  • You must be a U.S. citizen or permanent resident and have lived in the United States for at least five consecutive years to be covered by Medicare.
  • Your first premium payment is usually deducted from your Social Security check starting the month your coverage begins, or you receive a bill if you are not yet collecting Social Security.

How the Initial Enrollment Period determines your start date

Your Initial Enrollment Period is a seven-month window centered on the month you turn 65. It runs from three months before your birthday month through three months after. If you sign up during this window, your Part A and Part B coverage will start on the first of the month you turn 65 with no delay.

For example, if you turn 65 in June, your Initial Enrollment Period runs from March through September. If you sign up in April, May, June, July, August, or September, your coverage begins June 1. There is no waiting period.

Social Security automatically enrolls most people in Part A and Part B during their Initial Enrollment Period if they are already receiving Social Security benefits. If you are not yet collecting Social Security, you must sign up yourself through Medicare.gov, by phone at 1-800-MEDICARE, or at your local Social Security office.

What happens if you sign up after your Initial Enrollment Period ends

If you miss your Initial Enrollment Period and sign up late, your coverage start date shifts forward. Part A coverage usually begins the first of the month after you sign up. Part B coverage may not start until several months later, depending on when you enroll.

For Part B specifically, if you sign up between April and December of the year you turn 65 (after your Initial Enrollment Period has ended), your coverage begins the following January 1. If you sign up in January or later, your coverage begins the first of the month after you sign up.

Late enrollment also triggers a permanent premium penalty on your Part B premiums. You pay an extra 10 percent for each full 12-month period you were may be able to access but not enrolled. This penalty stays with you for life, even if you later switch to a different plan. The penalty is calculated on the standard Part B premium amount each year, which changes annually.

Enrollment important date and how they affect your start date

Missing key important date can delay your coverage by months. Your Initial Enrollment Period is the easiest window: sign up anytime during those seven months and coverage starts the first of your birthday month.

If you miss the Initial Enrollment Period, you can still sign up during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage from a General Enrollment Period sign-up begins July 1 of that year. This means if you sign up in January, you wait until July. If you sign up in March, you still wait until July.

Some people may have access to for a Special Enrollment Period, which allows you to sign up outside the normal windows without penalty. You may may have access to if you lose employer coverage, move out of your plan's service area, or experience certain life events. If you have a Special Enrollment Period, your coverage start date depends on when you sign up and which plan you choose — ask Medicare or your plan directly for the exact date.

How Part A and Part B start dates can differ

In most cases, Part A and Part B start on the same date. However, they can start separately if you sign up at different times or if you decline one of them.

For example, if you are still working and your employer offers health insurance, you may decline Part B during your Initial Enrollment Period to avoid paying premiums while you have group coverage. Your Part A coverage still begins on the first of your birthday month. When you later sign up for Part B (perhaps after you retire), Part B will start on a different date — usually the first of the month after you sign up, or July 1 if you sign up during General Enrollment.

If you decline Part A during your Initial Enrollment Period, you can sign up later during General Enrollment. Part A coverage will then begin July 1 of the year you enroll, separate from any Part B start date.

What to expect in the weeks before your coverage starts

About two weeks before your coverage begins, you will receive your Medicare card in the mail. The card shows your Medicare number, which you will use to identify yourself to doctors, hospitals, and pharmacies. Keep this card in a safe place and bring it to all medical appointments.

You will also receive a document called "Your Medicare Coverage" or a similar welcome packet that explains what is covered under Part A and Part B, what you pay, and how to use your benefits. Read this carefully so you know what to expect on your first day of coverage.

If you enrolled in a Medicare Advantage plan or a prescription drug plan, you will receive separate materials from that plan. These materials explain your plan's specific rules, copayments, and how to find in-network providers.

Your first premium payment and how it is collected

If you are already receiving Social Security when your Medicare coverage begins, your Part B premium is automatically deducted from your monthly Social Security payment. You will see the deduction listed on your Social Security statement.

If you are not yet collecting Social Security, Medicare will send you a bill for your Part B premium. You can pay by mail, phone, or online through Medicare.gov. Part A has no monthly premium for most people, so you will not receive a bill for Part A.

Your first premium is usually due by the end of the month your coverage begins. If you do not pay on time, your coverage may be delayed or cancelled. If you have financial hardship, contact Medicare to discuss payment options.

Frequently Asked Questions

If I turn 65 on the last day of the month, does my coverage start that day or the next month?

Your coverage starts on the first day of the month you turn 65, not on your birthday. If you turn 65 on January 31, your coverage begins January 1. If you turn 65 on February 28 or 29, your coverage begins February 1.

Can I delay my Medicare start date if I am still working?

You cannot delay your Part A start date — it begins automatically on the first of your birthday month. However, you can decline Part B if you have employer health insurance and are still working. When you later enroll in Part B, it will start on a different date. Be aware that delaying Part B past your Initial Enrollment Period triggers a permanent premium penalty.

What if I do not receive my Medicare card before my coverage starts?

Your coverage begins on the scheduled date even if your card has not arrived. You can use your Social Security number as your Medicare number at the doctor or hospital while you wait for the card. If your card does not arrive within two weeks of your start date, contact Medicare at 1-800-MEDICARE to request a replacement.

Does my prescription drug coverage start on the same date as Part A and Part B?

If you enroll in a standalone prescription drug plan during your Initial Enrollment Period, coverage usually begins January 1 of the year after you turn 65, not the first of your birthday month. If you enroll in a Medicare Advantage plan that includes drug coverage, the start date matches your Part A and Part B start date. Check your enrollment confirmation to confirm your plan's start date.

What happens to my coverage if I move to a different state?

Your Part A and Part B coverage continues in any state. However, if you are enrolled in a Medicare Advantage plan or prescription drug plan, you may need to switch plans because many plans do not cover out-of-state. Contact your plan or Medicare before you move to understand your options and any changes to your coverage date.