When should you sign up for Medicare?

What you need to know

Your Initial Enrollment Period

It lasts 7 months: the 3 months before the month you turn 65, your birthday month, and the 3 months after. If your birthday is on the 1st, Medicare treats you as turning 65 the month before, so everything moves up one month.

When coverage starts

Premium-free Part A starts the month you turn 65. Part B starts that same month if you sign up before your birthday month. If you sign up in your birthday month or later, it starts the first day of the month after you sign up.

Still working?

If you or your spouse are covered by a job with 20 or more employees, that plan pays first and you can usually wait on Part B with no penalty. You'll get an 8-month Special Enrollment Period starting when the job or the coverage ends, whichever comes first. COBRA and retiree coverage don't count as job-based coverage, and COBRA doesn't extend that window. If the employer has fewer than 20 employees, Medicare usually pays first, so you generally need Part A and Part B when you're first eligible.

HSA contributions

Once you have any part of Medicare, you can't contribute to an HSA. If you sign up for premium-free Part A after 65, it can be backdated up to 6 months (but not before the month you turned 65), so stop HSA contributions 6 months before you enroll.

Missed your window?

The General Enrollment Period runs January 1 to March 31 each year, with coverage starting the month after you sign up. Late penalties may apply.

Every year after

Open Enrollment runs October 15 to December 7, with changes starting January 1. If you're in a Medicare Advantage plan, you can switch plans or go back to Original Medicare January 1 to March 31.

Medicare Supplement (Medigap)

Your 6-month Medigap Open Enrollment starts the first month you're 65 or older and have Part B. During it, federal law guarantees you can buy any Medigap policy sold in your state, regardless of health. After it ends, you may be turned down or charged more.

How to sign up

Online at ssa.gov/medicare/sign-up, by phone at 1-800-772-1213 (TTY 1-800-325-0778), or at a local Social Security office. Railroad retirees call the RRB at 1-877-772-5772.