When Medicare Starts: Enrollment Deadlines and Coverage Dates

Medicare coverage begins on the first day of the month you turn 65

If you turn 65 on any day of the month, your Medicare Part A (hospital insurance) and Part B (medical insurance) coverage starts on the first day of that same month. You do not have to wait until your birthday passes. This is true whether you were born on the first of the month or the last day.

The key date is when you enroll, not when coverage starts. If you enroll during your Initial Enrollment Period — which runs for seven months centered on the month you turn 65 — you will have no gap in coverage and no late penalties. If you miss this window, coverage delays and permanent surcharges may explore.

Key Takeaways

• Medicare Part A and Part B coverage begins on the first of the month you turn 65, regardless of the day of the month you were born.
• Your Initial Enrollment Period is seven months long: three months before the month you turn 65, the month you turn 65, and three months after.
• If you enroll before your 65th birthday, coverage still does not start until the first of the month you turn 65.
• Missing your Initial Enrollment Period triggers a permanent 10 percent surcharge on Part B premiums for each year you delayed, and a similar surcharge on Part D (prescription drug) coverage.
• If you are still working and have employer health insurance, you may be able to delay Part B enrollment without penalty under specific circumstances.

Your Initial Enrollment Period: The seven-month window

The Initial Enrollment Period starts three months before the month you turn 65 and ends three months after. For example, if you turn 65 in June, your enrollment period runs from March through September. You can enroll any time during these seven months, and coverage will start on June 1 — the first of the month you turn 65.

Enrolling early (in March, April, or May in this example) does not move your coverage start date forward. Coverage always begins on the first of the month you turn 65. The advantage of enrolling early is that you avoid the rush and reduce the chance of missing the important date.

You can enroll through Medicare.gov, by phone at 1-800-MEDICARE, by mail, or in person at your local Social Security office. If you enroll by the 15th of any month, your coverage will start on the first of the next month (or the first of your 65th birthday month if you are still within your Initial Enrollment Period).

What happens if you miss your Initial Enrollment Period

If you do not enroll during your seven-month Initial Enrollment Period, you will face a permanent penalty on your Part B premiums. The surcharge is 10 percent of the standard Part B premium for each full 12 months you were may be able to access but not enrolled. If you delayed for two years, you pay 20 percent more than the standard rate for the rest of your life.

The same penalty applies to Part D (prescription drug) coverage. If you go without creditable drug coverage for 63 days or more, you will owe a surcharge when you finally enroll. The amount depends on how long you went without coverage.

There is no way to remove these penalties once they are applied. They do not expire. This is why enrolling on time, even if you do not plan to use Medicare when ready, is important.

Special Enrollment Period: If you have employer coverage

If you are still working at 65 and your employer has 20 or more employees, you may be able to delay Part B enrollment without penalty. This is called the Special Enrollment Period. You must have health insurance through your employer or your spouse's employer, and that coverage must be considered "creditable" — meaning it covers at least as much as Medicare Part B.

To use this exception, you do not enroll in Part B during your Initial Enrollment Period. Instead, you enroll within eight months after your employment ends or your employer coverage stops, whichever comes first. When you do enroll, there is no late penalty, and coverage begins on the first of the month after you enroll.

You must still enroll in Part A at 65, even if you have employer coverage. Part A has no premium for most people, and delaying it can result in a penalty. Part D (prescription drug) coverage does not have the same employer exception, so if you do not have creditable drug coverage through your employer, you should enroll in Part D during your Initial Enrollment Period to avoid a surcharge.

Part A versus Part B: Different start dates and rules

Part A (hospital insurance) covers inpatient hospital stays, skilled nursing facility care, hospice, and some home health services. It starts on the first of the month you turn 65. Most people do not pay a premium for Part A if they or their spouse paid Medicare taxes for at least 10 years.

Part B (medical insurance) covers doctor visits, outpatient care, and some preventive services. It also starts on the first of the month you turn 65, but only if you enroll during your Initial Enrollment Period. If you delay Part B and do not may have access to for the Special Enrollment Period exception, your coverage will not start until the first of the month after you enroll — and you will owe the permanent surcharge.

Part A and Part B are separate from each other. You can enroll in Part A without Part B, but most people enroll in both. If you decline Part B during your Initial Enrollment Period and change your mind later, you can enroll in Part B during the General Enrollment Period (January 1 through March 31 each year), but coverage will not start until July 1 of that year, and you will owe the late penalty.

Part D and Medigap: Enrollment important date tied to Medicare start

Part D (prescription drug coverage) enrollment is separate from Part A and Part B, but the important date is the same: your Initial Enrollment Period. If you do not enroll in Part D during this seven-month window and you do not have other creditable drug coverage, you will owe a surcharge when you eventually enroll. The surcharge is 1 percent of the national average Part D premium for each month you were without coverage.

Medigap (supplemental insurance) helps pay for costs that Medicare does not cover, such as copayments and coinsurance. You can enroll in Medigap at any time, but the best time is during your Medigap Open Enrollment Period, which is six months starting the month you turn 65 and enroll in Part B. During this window, insurers cannot deny you coverage or charge you more based on your health history. If you enroll in Medigap after this period, you may face higher premiums or medical underwriting.

Frequently Asked Questions

If I turn 65 on June 15, does Medicare start on June 1 or June 15?

Medicare starts on June 1, the first of the month you turn 65. The exact day of your birthday does not matter. You must be 65 by the end of the month for coverage to start on the first of that month.

Can I delay Medicare if I am still working?

You can delay Part B if you have employer coverage with 20 or more employees and that coverage is creditable. You must still enroll in Part A at 65. Part D does not have an employer exception, so if you want to avoid a surcharge, you should enroll in Part D during your Initial Enrollment Period even if you are still working.

What if I miss the important date by one month?

If you miss your Initial Enrollment Period by even one month, you will owe a permanent 10 percent surcharge on Part B premiums. Coverage will not start until the first of the month after you enroll. There is no grace period or exception for being one month late.

Do I have to enroll in Medicare if I am still working and have health insurance?

You must enroll in Part A at 65 (it has no premium for most people). You can delay Part B if you have employer coverage, but you should enroll in Part D during your Initial Enrollment Period to avoid a drug coverage surcharge. Check with your employer's benefits office about whether your coverage is considered creditable.

When does Medigap coverage start if I enroll at the same time as Medicare?

Medigap coverage typically starts on the first of the month after you enroll, or on the first of the month you turn 65 if you enroll before that date. The exact date depends on the insurance company. Contact the insurer directly to confirm when your coverage begins.