Medicare Enrollment Window

2026 premiums · reviewed September 5, 2026

Dates your Medicare sign-up window to your birth month and shows what a late sign-up costs for life. About

In plain words. You can sign up for Medicare during a seven-month window around your 65th birthday: three months before your birthday month, that month, and three months after. When your coverage starts depends on when in the window you sign up. Miss it without employer coverage and you wait for a once-a-year period and pay a penalty on every premium for the rest of your life. This tool gives you the dates and the penalty.

Why it matters. The penalties are permanent and the window is easy to miss, especially for people still working. The dates are the whole answer for most people.

An example. Someone born in June signs up in March, April, or May and is covered from June 1. Someone who signs up two full years late pays 20 percent more for Part B every month for life: about $41 a month extra on this year's premium.

Where it stops. It assumes no employer coverage; if you or your spouse still work for a company with 20 or more employees, the window extends to eight months after that coverage ends, with no penalty. Medigap and Medicare Advantage plans have their own sign-up windows. Everything it leaves out.

Birth month

Birth year

Day of the month you were born

Any other dayThe 1st of the month

A birthday on the first of a month moves the whole calendar one month earlier.

Your first window to sign up for Medicare (the initial enrollment period)

March to September 2027

Sign up in March, April, or May and your coverage starts June 2027. Sign up in June or later and it starts the month after you do, which could be as late as October 2027.

Month you become eligible for Medicare: June 2027; Your 65th birthday month
Next chance if you miss the window: January to March 2028; The general enrollment period. Coverage starts the month after you sign up.
Tax year that sets your first premium: 2025; Medicare uses that year's tax return to decide whether you pay an income-based surcharge

What signing up late costs, for life

Months late for Part B

Months after your window closed with no Part B and no employer coverage. Only full 12-month periods count.

Months without drug coverage

Months with no Part D and no other drug coverage Medicare accepts, once a gap reaches 63 days.

Part B penalty each month: $0.00 / month; Less than one full year late, so no penalty
Part B penalty over 20 years: $0; At today's premium. It rises as the premium does.
Part D penalty each month: $0.00 / month; No months without drug coverage

Still covered by an employer plan from a company with 20 or more workers, yours or your spouse's? You get a special window of 8 months after that coverage or the job ends, with no penalty. COBRA and retiree plans do not count.

This follows the enrollment periods and late penalties as Medicare.gov describes them, using the 2026 Part B premium of $202.90 and the Part D base premium of $38.99. It leaves out Part A, which is free for most people, and the separate windows for Medicare Advantage, Medigap, and Medicare before 65 through disability. Educational, not advice.

This is a simplified model, not your actual tax return or plan. It only knows what you type in, leaves out rules that may apply to you, and cannot weigh the other facts and trade-offs a real decision depends on. Before you act, talk with a professional who knows your whole situation.

Educational only, not investment, tax, or legal advice. Results are hypothetical estimates that vary with each use and over time and are not guaranteed accurate or complete. Using this tool creates no client relationship with Considerate Capital, and the site that linked here is not affiliated with it. By using it you agree to the tool terms.