Medicare Enrollment Window: the facts

1. The initial enrollment period is seven months: the 3 months before the month you turn 65, that month, and the 3 after. A birthday on the first of a month moves everything one month earlier.
2. Sign up in the three months before and coverage begins the first of your birthday month; sign up in the birthday month or the three after and it begins the month after you sign up.
3. Miss the window without employer coverage and the next chance is the general enrollment period, January 1 to March 31, with coverage the month after signing up: up to a year without Part B.
4. The Part B late penalty is 10 percent of the standard premium for each full 12-month period without it, for as long as you have Medicare. Two years late is 20 percent: $40.58 a month on the 2026 premium of $202.90, every month, for life.
5. The Part D penalty is 1 percent of the national base beneficiary premium ($38.99 for 2026) for each month without creditable drug coverage after a gap of 63 days or more, rounded to the nearest ten cents, and it is recomputed each year on that year's base premium: 14 months is $5.50 a month.
6. Still working with employer coverage from a firm of 20 or more? The special enrollment period runs 8 months after the coverage or the employment ends, whichever is first, with no penalty; COBRA and retiree coverage do not count as employer coverage for this purpose.

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