Quick answer: Most people should sign up for Medicare during the Initial Enrollment Period: the 7-month window that starts 3 months before the month you turn 65 and ends 3 months after. Open Enrollment for changing plans runs October 15 to December 7 every year.
Key Takeaways
- Initial Enrollment Period is the 7 months around your 65th birthday
- Open Enrollment runs October 15 to December 7
- Late Part B and Part D enrollment carries lifetime penalties
- Working past 65 with employer coverage allows a Special Enrollment Period
Initial Enrollment Period (IEP)
If you already receive Social Security, you are enrolled in Parts A and B automatically. Otherwise, apply at ssa.gov/medicare. Enrolling in the three months before your birthday month means coverage starts the first day of your birthday month.
Special Enrollment Period (SEP)
If you or your spouse are still working and covered by an employer group plan at 65, you can delay Part B without penalty and enroll within 8 months after that coverage ends. COBRA and retiree coverage do not count as active employment coverage.
General Enrollment Period
If you missed both windows, you can enroll January 1 to March 31. Coverage starts the month after you sign up, and a late-enrollment penalty may apply.
Annual Open Enrollment (October 15 – December 7)
Switch between Original Medicare and Medicare Advantage, change Advantage plans, or join, drop, or switch Part D drug plans. Changes take effect January 1.
Medicare Advantage Open Enrollment (January 1 – March 31)
If you are already in an Advantage plan, you can switch to another Advantage plan or go back to Original Medicare once during this window.
Late penalties to know
- Part B: 10% added to the premium for each full 12-month period you were eligible but did not enroll, for life.
- Part D: 1% of the national base premium for each month without creditable drug coverage, for life.
FAQ
Is Medicare free? Part A is premium-free for most people who paid Medicare taxes for 10 years; Part B has a monthly premium that changes annually.
Do I need to enroll if I have VA coverage? VA benefits do not replace Medicare; many veterans enroll in both.
Where can I compare plans? Use the official Plan Finder at medicare.gov/plan-compare.
Sources
Last updated: August 16, 2026. Written by the InfoBrief Editorial team. We link to official government and company sources and update articles when facts change. See our disclosure.