Do You Get Part A Automatically?
According to Medicare & You 2026, if you're already receiving benefits from Social Security or the Railroad Retirement Board (RRB), you'll automatically get Part A and Part B starting the first day of the month you turn 65. Your red, white, and blue Medicare card arrives in the mail about 3 months before your 65th birthday.
If your birthday is on the first day of the month, your coverage starts the first day of the prior month.
According to Medicare & You 2026, if you're under 65 and have a disability, you'll get Part A and Part B automatically after receiving 24 months of disability benefits from Social Security or certain RRB disability benefits. If you have ALS (amyotrophic lateral sclerosis), you get Part A and Part B automatically the month your Social Security disability benefits begin.
The Initial Enrollment Period (IEP)
If you're turning 65 and are NOT already receiving Social Security or RRB benefits, you need to actively sign up for Medicare. Your chance to do this is called the Initial Enrollment Period (IEP).
According to Medicare & You 2026, the IEP is a 7-month window: it begins 3 months before the month you turn 65, includes the month you turn 65, and ends 3 months after that month.
If you turn 65 on June 2, your 7-month IEP begins in March and ends in September. If you turn 65 on June 1 (the first of the month), your IEP begins in February and ends in August.
When Does Your Coverage Start?
When your coverage begins depends on when during your IEP you sign up, according to Medicare & You 2026:
Coverage begins the first day of your birthday month. (If your birthday is on the 1st, coverage starts the first day of the prior month.)
Coverage starts the first day of the month after you sign up — so there may be a short delay.
You'll need to wait for a Special Enrollment Period or the General Enrollment Period (January 1–March 31 each year). Coverage won't start right away and you may face a late enrollment penalty if you have to buy Part A.
If You're Still Working at 65
This is where people most commonly get confused — and where a mistake can cost you. Your situation depends on your employer's size and the type of coverage you have.
Your employer plan pays first. You can delay Part B without penalty. But most people still sign up for premium-free Part A since it costs nothing. Talk to your HR department about how coordination works.
Medicare pays first. You should sign up for both Part A and Part B at 65, or Medicare won't cover what your small employer plan expects it to — and you could have large gaps in coverage.
COBRA is NOT considered coverage based on current employment. It does not qualify you for a Special Enrollment Period. Sign up for Medicare when you're first eligible. Missing this because of COBRA is one of the most expensive mistakes people make.
Marketplace coverage does not count as qualifying employer coverage. Once you're eligible for premium-free Part A, you'll lose eligibility for Marketplace subsidies. You should sign up for Medicare when you're first eligible.
The Special Enrollment Period (SEP)
If you delayed enrollment because you had qualifying group health plan coverage based on your or your spouse's current employment, you qualify for a Special Enrollment Period. According to Medicare & You 2026, you can sign up for Part A and/or Part B during the SEP at any time while you're still covered by the group health plan, or during the 8-month period that begins the month after the employment ends or the coverage ends — whichever comes first.
Your Special Enrollment Period begins when your employment or group health plan coverage ends — whichever happens first. You have 8 months. After those 8 months, you lose this window. COBRA coverage does not extend it. If you retire and go on COBRA, your SEP clock is already ticking from the day you left work, not from when COBRA ends.
The General Enrollment Period
If you missed your IEP and don't qualify for a Special Enrollment Period, you can sign up during the General Enrollment Period, which runs January 1 through March 31 each year. Coverage starts the first day of the month after you sign up. You may also face a late enrollment penalty if you have to buy Part A.
Health Savings Accounts (HSAs) and Medicare
This is an area where the timing of your enrollment matters for tax reasons. According to Medicare & You 2026, you cannot make contributions to an HSA after you have Medicare. Premium-free Part A coverage can go back retroactively 6 months from when you sign up or apply for Social Security benefits — which means your HSA contributions could be affected sooner than you think. Review the HSA contribution timing carefully before you apply for Medicare, and consider speaking with a tax advisor.
Where to Sign Up
You can sign up for Part A at SSA.gov/medicare/sign-up, or by contacting Social Security 3 months before you turn 65. If you worked for a railroad, visit RRB.gov or call 1-877-772-5772.
"The COBRA situation is the one that gets people the most. Someone retires in March, goes on COBRA through their former employer, and figures they have until COBRA ends to deal with Medicare. But your Special Enrollment Period started the day you left work — not the day COBRA runs out. I've seen people face months-long gaps in coverage and permanent premium penalties because of this. Please call me before you retire so we can get this right."
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