There are several situations in which you can sign up for Medicare Parts A and B. Each enrollment period has certain rules about when you can apply and when your coverage will start.
Initial Enrollment Period
When you turn age 65, you can join Medicare Parts A and B (and Parts C and/or D) during your Initial Enrollment Period. This is the seven-month period that starts three months before you turn 65, includes the month you turn 65, and ends three months after you turn 65.
Example: seven-month Initial Enrollment Period for someone with a July birthday. | ||||||
|---|---|---|---|---|---|---|
3 months before birthday month | Birthday month | 3 months after birthday month | ||||
April | May | June | July  | August | September | October |
Medicare starts first day of your | Medicare starts first day of the next month | Medicare starts the first day of the next month | ||||
Note: The later you enroll, the later your coverage will start. In this example, if your birthday is in July, your Initial Enrollment Period starts April 1 and ends Oct. 31.
Special Enrollment Period for Parts A and B
Some people with health care coverage through their job or union, or through their spouse's job or union, wait to sign up for Medicare Part A (hospital insurance) and/or Part B (medical insurance). If you or your spouse are actively working for an employer with more than 20 employees when you turn 65, you can get a Special Enrollment Period (SEP) to sign up for Parts A and/or B:
- Any time you're still covered by the employer or union group health plan through you or your spouse’s current employment; or
- During the eight months following the month the employer or union group health plan coverage ends, or when the employment ends (whichever is first).
If you delay enrolling even longer, you may have to wait for coverage and you may pay a lifetime late enrollment penalty surcharge on your Medicare premiums.
If you're under age 65, and eligible for Medicare because you're disabled and working (or you have coverage from a working family member), the SEP rules also apply to you as long as the employer has more than 100 employees.
General Enrollment Period
If you miss your Initial Enrollment Period or your Special Enrollment Period, you'll have another chance to enroll during the General Enrollment Period.
You can sign up for Medicare Parts A and B every year between Jan. 1 and March 31. Your coverage then starts the month following signing up. You may have a lifetime late enrollment penalty surcharge on your Medicare premiums.
Open Enrollment Period
The Open Enrollment Period (OEP) runs each year from Oct. 15 through Dec. 7. During this time, anyone:
- With Medicare Parts A and B can switch to a Part C (Medicare Advantage) plan.
- With a Medicare Part C (Medicare Advantage) plan can switch back to Medicare Parts A and B (Original Medicare).
- Who has or is signing up for Medicare Parts A and B can join, drop, or switch a Part D prescription drug plan.
- Who has or is signing up for Medicare Parts A and B can join, drop, or switch a Part C (Medicare Advantage) plan.
- With a Medicare Part C (Medicare Advantage) plan can switch to a new Medicare Part C plan.
Your coverage starts Jan. 1 of the following year.