Medicare is available to most Americans at 65, but it does not always start automatically, and the rules for when to sign up can be confusing, especially for people who are still working. Getting the timing wrong can cost you permanently higher premiums and months without coverage. This guide walks through the Medicare enrollment periods, explains who must act and when, and shows how to avoid late enrollment penalties.
The parts of Medicare in brief
- Part A covers inpatient hospital care, skilled nursing facility care after a qualifying hospital stay, hospice, and some home health care. Most people pay no premium because they or a spouse paid Medicare taxes for at least 40 quarters.
- Part B covers doctor visits, outpatient care, preventive services, durable medical equipment, and many infusions. Most people pay a standard monthly premium set each year, with higher amounts for people with higher incomes under IRMAA, the income-related monthly adjustment amount.
- Part C, Medicare Advantage, is an alternative way to receive Part A and Part B benefits through private plans, often with drug coverage.
- Part D covers outpatient prescription drugs through private plans.
Are you enrolled automatically?
If you are already receiving Social Security or Railroad Retirement Board benefits at least four months before turning 65, you will generally be enrolled in Part A and Part B automatically, with coverage starting the first day of your birthday month. Your Medicare card arrives about three months in advance. You can decline Part B if you have qualifying employer coverage.
If you are not yet receiving Social Security, which is common because full retirement age is now 66 to 67, you must sign up yourself through Social Security, online, by phone, or at a local office.
Initial Enrollment Period
Your Initial Enrollment Period (IEP) is seven months long: the three months before the month you turn 65, your birthday month, and the three months after. If you sign up during the three months before your birthday month, coverage starts the first day of your birthday month. Since 2023, if you sign up during your birthday month or the three months after, coverage starts the first day of the month after you sign up, which removed the longer delays that existed under the old rules.
Practical tip: sign up during the three months before your birthday month to avoid any gap.
Working past 65: the Special Enrollment Period
If you or your spouse are still working and you have group health coverage based on that current employment, you may be able to delay Part B without penalty. The size of the employer matters:
- Employer with 20 or more employees: the group plan is generally primary, and Medicare is secondary. Many people delay Part B and sometimes Part A.
- Employer with fewer than 20 employees: Medicare is generally primary. If you do not enroll in Part B, the employer plan may pay little or nothing for services Medicare would have covered. Most people in this situation should enroll in Part B at 65.
When your employment or the group coverage ends, whichever comes first, you have an eight-month Special Enrollment Period to enroll in Part B without penalty. You will need your employer to complete form CMS-L564, Request for Employment Information, or provide other proof of coverage.
Coverage that does not count
These types of coverage do not qualify you to delay Part B without penalty:
- COBRA continuation coverage
- Retiree health coverage
- Marketplace (ACA) coverage
- VA health care
- TRICARE, which generally requires Part B to remain in effect, with some exceptions
People on COBRA often make costly mistakes. The eight-month SEP clock starts when employment ends, not when COBRA ends. If you wait until COBRA runs out after 18 months, you will have missed the SEP and may owe a penalty.
Health Savings Accounts
If you contribute to an HSA, note that enrolling in any part of Medicare, including premium-free Part A, ends your eligibility to contribute. Part A coverage can be retroactive up to six months when you enroll after 65, so many advisors suggest stopping HSA contributions six months before you plan to enroll to avoid excess contributions.
General Enrollment Period
If you miss your IEP and do not qualify for an SEP, you can enroll during the General Enrollment Period, January 1 through March 31 each year. Coverage begins the first day of the month after you sign up. You may owe a late enrollment penalty.
Exceptional Special Enrollment Periods
CMS has created additional SEPs for specific situations, such as when an employer or health plan gave you misleading information, when you were affected by a natural disaster or emergency, when you were incarcerated, or when you lost Medicaid coverage. These can help people who missed a deadline for reasons beyond their control.
Late enrollment penalties
Part B penalty
For each full 12-month period you could have had Part B but did not sign up, your monthly premium increases by 10 percent of the standard premium. The penalty usually lasts as long as you have Part B. For example, delaying 30 months without qualifying coverage produces two full 12-month periods and a 20 percent penalty for life.
Part A penalty
Most people get premium-free Part A, so there is no penalty. If you must buy Part A and delay, your premium may increase by 10 percent for twice the number of years you delayed.
Part D penalty
If you go 63 or more consecutive days without Part D or other creditable drug coverage after your IEP ends, you may owe a penalty calculated as 1 percent of the national base beneficiary premium multiplied by the number of uncovered months. The penalty is added to your Part D premium for as long as you have Part D. Employer drug plans must tell you each year whether they are creditable. Extra Help enrollees do not pay the Part D penalty.
Medigap open enrollment
The six-month Medigap open enrollment period begins the month you are 65 or older and enrolled in Part B. During this window, insurers in most states must sell you any Medigap policy they offer without medical underwriting. After it ends, insurers in most states can deny coverage or charge more based on health. This makes Part B timing important for people who plan to buy Medigap.
Medicare Advantage and Part D annual periods
- Annual Open Enrollment: October 15 to December 7, for switching between Original Medicare and Medicare Advantage or changing Part D plans.
- Medicare Advantage Open Enrollment: January 1 to March 31, for people already in a Medicare Advantage plan.
- Special Enrollment Periods: for moves, loss of coverage, Extra Help eligibility, and other events.
A simple timeline checklist
- Age 64 and 9 months: decide whether to enroll in Part B now or delay based on employer coverage.
- Three months before your birthday month: enroll in Part A and B through Social Security if you are not automatically enrolled.
- During your IEP: choose Part D or Medicare Advantage.
- Within six months of Part B start: buy Medigap if desired.
- When you retire later: enroll in Part B within eight months of losing employment-based coverage, and in Part D within 63 days.
Frequently Asked Questions
Can I get Medicare before 65?
Yes, if you have received Social Security Disability Insurance for 24 months, or you have end-stage renal disease or ALS. People with ALS get Medicare the month their disability benefits begin.
Should I take Part A if I am still working?
Many people take premium-free Part A at 65 even while working because it can act as secondary coverage. Exceptions include people contributing to an HSA.
Can a penalty be removed?
If you believe the penalty is wrong, for example because you had qualifying coverage, you can request reconsideration and provide proof.
This article is for general informational purposes only and is not legal, medical, tax, or financial advice. Rules vary by state and change over time; confirm details with the relevant agency or a licensed professional.
