Last verified: April 19, 2026.
Medicare Initial Enrollment Period (IEP)
Your seven-month window around your 65th birthday to enroll in Medicare without late penalties.
What this window is
A seven-month window that begins three months before the month a person turns 65, includes the birth month, and ends three months after. Coverage effective dates vary depending on when in the window enrollment is completed.
What triggers it
Approaching the 65th birthday. The window opens the first day of the third month before the birth month and closes the last day of the third month after.
What happens if you miss it
Late enrollment in Part B can carry a permanent monthly premium surcharge of 10 percent for each full 12-month period the beneficiary was eligible but not enrolled, with limited exceptions for people who delayed because of qualifying employer group coverage. Late enrollment in Part D carries a separate permanent monthly surcharge based on the national base premium and the number of uncovered months.
Why this matters
The Initial Enrollment Period is the single best opportunity most people will ever have to enroll in Medicare cleanly. Enrolling during the IEP avoids permanent late enrollment penalties for Part B and Part D, preserves access to the Medigap Open Enrollment Period, and gives you a clean start with an effective date that matches the month you turn 65 in most cases.
How to verify these claims
Every claim on this page traces to a primary federal source listed in the reference card below. URLs are re-verified on the cadence shown at the top of the card.
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