Your Medicare Initial Enrollment Period usually lasts seven months: the three months before the month you turn 65, your birthday month, and the three months afterward.
The Initial Enrollment Period is the seven-month window when most people can first sign up for Medicare around age 65. Missing it can lead to delayed coverage and, in some cases, lasting penalties.
How the Seven-Month Window Works
For most people, the window includes:
- Three months before the month you turn 65
- The month you turn 65
- Three months after your birthday month
For example, if you turn 65 on July 15, 2027, the period generally runs from April 1 through October 31, 2027.
If you turn 65 on July 1, 2027, Medicare generally treats June as your eligibility month: the seven-month period is March through September. Signing up in March, April, or May can allow coverage to start June 1.
When Does Coverage Start?
If you enroll in Part B or Part A that you pay a premium for during the three months before your birthday month, coverage generally starts the month you turn 65.
If you enroll during your birthday month or one of the following three months, coverage generally starts the next month.
When you are enrolled on time, premium-free Part A generally starts the month you turn 65 and may start the month before if your birthday is on the first. If your birthday is on the first of the month, use the earlier month when working out your Part B start date, as the example above shows.
Medicare's coverage-start guide gives timing for different situations.
Will Enrollment Be Automatic?
You may be enrolled automatically if you receive Social Security or Railroad Retirement Board benefits before 65. Otherwise, you generally need to apply through Social Security.
Even with automatic Part A and Part B enrollment, you still need to decide how to receive coverage and whether to add drug coverage.
Can You Delay Enrollment?
You may be able to delay Part B without a penalty if you have coverage from your or your spouse's current employment. Before waiting, ask which insurer will pay first and whether your job-based coverage allows you to enroll later without a penalty.
COBRA, retiree coverage, and Marketplace coverage do not necessarily create the same Part B enrollment protection. Confirm the rules before delaying.
What Should You Do During This Period?
- Confirm whether enrollment is automatic
- Apply for Part A and Part B if necessary
- Compare Original Medicare and Medicare Advantage
- Arrange Part D or check that your other drug coverage is creditable, meaning it is expected to pay at least as much as standard Medicare drug coverage
- Consider Medigap timing
- Coordinate the end of existing insurance
- Check doctors, hospitals, and prescriptions
This age-65 timeline is separate from disability-based enrollment. If you already have Part A and Part B before 65, you generally do not apply for them again merely because of your birthday. You may have new private-plan or Medigap enrollment opportunities. Check these opportunities even if your Part A and Part B coverage is already in place.
Medicare policy sources last checked: October 8, 2026.