Turning 65 in 2026 forces a decision that trips up more people than any other Medicare milestone: enroll now, or wait? The default assumption that Medicare enrollment automatically happens is wrong for most workers. Social Security only auto-enrolls people already collecting retirement benefits; everyone else has to actively sign up at SSA.gov during a specific window. The stakes are high in both directions. Enroll when you do not need to and you may pay for Part B on top of an existing employer premium for no added benefit. Delay when you should not and the Part B late penalty adds 10% to your premium for every 12-month period you went without coverage, for the rest of your life. Getting this decision right depends almost entirely on one variable: what other coverage you have on the day you turn 65. This single question, active employer group coverage or something else, determines whether the safest move is to sign up immediately or to legitimately wait, and confusing the two paths is the single most expensive mistake a new Medicare-eligible person can make in 2026. Insurance brokers, HR departments, and even some Social Security representatives routinely give incomplete answers, which is why a clear decision tree matters more than a generic checklist here.
Five coverage scenarios cover nearly everyone turning 65 in 2026: still working with large-employer coverage (20 or more employees), still working with small-employer coverage, on COBRA continuation, on an ACA Marketplace plan, or retired with no other coverage. Each scenario has a different correct answer, and this guide walks through the decision tree for all five, plus the documents you need and the exact deadlines for each path. Employer size is the hinge that the entire decision swings on: it determines whether Medicare pays primary or secondary, and that in turn determines whether delaying carries a penalty. Marketplace enrollees face a separate trap because premium tax credit eligibility usually disappears the moment someone qualifies for premium-free Part A, whether or not they actually enroll, which quietly turns a subsidized plan into a full-price plan. Before you decide, confirm your Medicare eligibility at the Medicare eligibility page, and if your income is limited, check the Medicaid income limits for 2026 to see whether dual Medicare and Medicaid coverage could eliminate most of your out-of-pocket costs. The federal poverty level figures for 2026 also determine whether a Medicare Savings Program can cover your Part B premium entirely.
6 Steps to Get Coverage
Common Mistakes That Cost People Thousands
The most expensive mistakes people make when deciding whether to enroll in Medicare at 65. Most of these consequences are permanent:
- Assuming COBRA, retiree coverage, or an ACA Marketplace plan lets you delay Part B without penalty. None of them qualify under Medicare Secondary Payer rules. Only active large-employer group coverage (20 or more employees) does.
- Keeping a subsidized ACA Marketplace plan after becoming eligible for premium-free Part A. Eligibility for premium-free Part A generally ends your premium tax credit eligibility, even if you never enroll in Medicare, leaving you paying full price for an ACA plan you no longer need.
- Enrolling in Part A while still contributing to an HSA. Any Medicare enrollment, including premium-free Part A, makes further HSA contributions ineligible under IRC Section 223 and can trigger an IRS excess-contribution penalty once Part A applies retroactively up to 6 months.
- Going 63 or more days without creditable drug coverage after becoming Medicare-eligible. This triggers a permanent Part D penalty of 1% per month of the national base premium, even if you never fill a prescription.
- Missing the 6-month Medigap guaranteed-issue window that starts the month you are both 65 and enrolled in Part B. After it closes, Medigap insurers in most states can deny you or charge more for pre-existing conditions.
- Waiting for a bill or a letter to prompt enrollment. Nobody sends a reminder besides Social Security's own mailings, and by the time a gap in coverage shows up, the IEP has often already closed.
Enroll Now vs Delay: Which Should You Choose?
Three coverage situations decide whether enrolling now or delaying makes sense in 2026. Active large-employer coverage (20 or more employees, yours or a spouse's) is the only situation that supports a penalty-free Part B delay; the employer plan pays primary, Medicare would pay secondary, and you get an 8-month Special Enrollment Period once that coverage ends. COBRA continuation coverage looks similar to active employer coverage on paper but does not qualify under Medicare Secondary Payer rules; anyone on COBRA at 65 should enroll in Part B during the IEP to avoid a lifetime penalty, even though the monthly bill from the COBRA administrator can look identical to what was withheld from a paycheck the month before. ACA Marketplace plans carry a hidden trap: becoming eligible for premium-free Part A typically ends premium tax credit eligibility even before you enroll in Medicare, so staying on a subsidized Marketplace plan past 65 usually means paying full price without realizing it, since the Marketplace does not automatically flag the change. Retiree health plans purchased directly from a former employer fall into the same non-qualifying category as COBRA and should not be treated as a reason to delay Part B.
Retirees with no other coverage face the simplest math: enroll in Parts A and B during the 7-month IEP, full stop. Waiting without a qualifying reason means a 10% per year Part B penalty that compounds for life, plus a coverage gap until the next General Enrollment Period (January 1 through March 31, with coverage now starting the month after enrollment per the BENES Act rather than the old July 1 rule). Workers who are actively contributing to a Health Savings Account (HSA) are the one group where delaying even Part A can make sense, because any Medicare enrollment stops future HSA contributions under IRC Section 223. Weigh the HSA's ongoing tax benefit against the cost of paying full employer premiums without Medicare's backup coverage before deciding to delay everything. Spouses add another layer: a younger spouse without their own Medicare eligibility often needs to stay on the working spouse's employer plan or the ACA Marketplace, which does not change the Medicare-eligible spouse's own enroll-or-delay decision but does affect the household's total premium math when comparing options side by side. Retirement itself is a qualifying life event for the non-Medicare spouse too, opening a 60-day window to enroll in a new Marketplace plan or a different employer plan if household coverage is shifting at the same time.
Documents You Need to Make the Enrollment Decision
Gathering the right paperwork before your 65th birthday month prevents the single most common cause of enrollment delays: incomplete Special Enrollment Period applications. If you plan to delay Part B because of active large-employer coverage, Social Security will eventually require Form CMS-L564 (Request for Employment Information), which your employer must complete to confirm your active coverage dates. Keep every notice your HR department sends confirming plan status, because you will need it months or years later when that 8-month window opens, often long after the original HR contact has moved on or the paperwork has been archived. Workers who assume they can request these records retroactively from a former employer frequently discover that turnover in the HR department, company mergers, or simple recordkeeping gaps make last-minute documentation far harder to obtain than expected. Building a small physical or digital folder the year you turn 65, and updating it every time your coverage status changes, removes nearly all of the friction from whichever enrollment path you eventually take.
- Social Security number and a government-issued photo ID for the SSA.gov application
- Form CMS-L564 (Request for Employment Information), completed by your employer, if delaying Part B due to active large-employer coverage
- Proof of work history (W-2s or Social Security earnings statement) to confirm premium-free Part A eligibility
- Your COBRA election notice or ACA Marketplace enrollment confirmation, showing your current coverage type and start date
- Annual Notice of Creditable Coverage for prescription drugs, from an employer plan or Marketplace plan, to avoid the Part D late penalty
- HSA plan summary and contribution records, if you are weighing whether to delay Medicare to keep contributing to a Health Savings Account
What Happens If You Get the Decision Wrong
Two permanent penalties enforce Medicare's enrollment deadlines. The Part B late enrollment penalty adds 10% to your monthly premium for every full 12-month period you were eligible but not enrolled, without a valid exemption, and that surcharge never expires. At the 2026 standard Part B premium of $202.90, two years of delay without a valid reason adds roughly $40.58 every month for the rest of your life, and that dollar figure only grows in future years as the base Part B premium itself rises. The Part D late enrollment penalty works similarly but is based on months rather than years: 1% of the national base beneficiary premium for every month you went without creditable drug coverage after first becoming eligible, even if you filled zero prescriptions during that gap. Both penalties attach to the person, not the plan, so switching insurers or plan types later does not erase either surcharge; it simply carries forward onto whatever new premium applies.
Beyond the financial penalty, missing the IEP without a qualifying SEP forces a wait for the General Enrollment Period, which runs January 1 through March 31 each year. Coverage now starts the first day of the month after you enroll during the GEP, a BENES Act improvement over the old rule that delayed coverage until every July 1 regardless of when in the window someone signed up. Still, a gap of weeks or months without Medicare while owing a permanent penalty is entirely avoidable by making the enroll-or-delay decision correctly the first time. Anyone unsure which category they fall into should call the State Health Insurance Assistance Program (SHIP) in their state for free, unbiased counseling before the IEP closes rather than after, since SHIP counselors cannot undo a penalty that has already been assessed but can prevent one from ever starting. Employer benefits administrators and insurance agents selling Medicare Advantage or Medigap plans are not a substitute for SHIP, since agents are compensated on enrollments rather than on giving neutral advice about whether enrolling now is even the right move.
Frequently Asked Questions
Should I enroll in Medicare if I am still working at 65?
Your employer's size decides the answer. If your employer (or your spouse's) has 20 or more employees and you have active group coverage, you can delay Part B penalty-free and get an 8-month Special Enrollment Period when that coverage ends. If your employer has fewer than 20 employees, Medicare becomes your primary payer at 65, so you should enroll in both Part A and Part B during your 7-month Initial Enrollment Period to avoid the permanent Part B late penalty.
Should I enroll in Medicare if I have COBRA coverage?
Yes. COBRA continuation coverage does not count as active employer coverage under Medicare Secondary Payer rules, no matter how similar it looks to your old plan. Anyone on COBRA at 65 should enroll in Part B during the 7-month Initial Enrollment Period. Delaying because of COBRA is one of the most common and most expensive mistakes, since it triggers a 10% per year lifetime Part B penalty with no exception.
Should I enroll in Medicare if I have an ACA Marketplace plan?
Yes, in almost every case. Becoming eligible for premium-free Part A generally ends your eligibility for ACA premium tax credits, even before you actually enroll in Medicare. Staying on a subsidized Marketplace plan past 65 often means paying full, unsubsidized price without realizing your credit is gone, and reconciling that mismatch on your next Form 1095-A can trigger a repayment of credits you were not actually entitled to receive. Enroll in Medicare during your Initial Enrollment Period and drop the Marketplace plan to avoid double-paying.
What happens if I don't enroll in Medicare when I turn 65?
If you do not have a valid Special Enrollment Period, missing your 7-month Initial Enrollment Period means waiting for the General Enrollment Period, which runs January 1 through March 31 each year, with coverage starting the first day of the month after you enroll. You will also owe a permanent Part B penalty of 10% for every full 12-month period you went without coverage, and possibly a Part D penalty of 1% per month for lack of creditable drug coverage.
Is Part A free, and should I take it even if I delay Part B?
Part A is premium-free in 2026 for most people with 10 or more years of Medicare-covered work history, and almost everyone should enroll in it at 65, even while delaying Part B for active large-employer coverage. The one exception is workers actively contributing to a Health Savings Account (HSA): any Medicare enrollment, including free Part A, stops further HSA contributions under IRC Section 223.
How do I know if my employer coverage lets me delay Medicare?
Ask HR to confirm your employer's total US employee count across all locations, including part-time staff. If the total is 20 or more, and you have active group health coverage (not retiree coverage or COBRA), you can delay Part B penalty-free. Get written confirmation of your employer's size and your active-coverage dates, since Social Security will require Form CMS-L564 completed by your employer when you eventually enroll under the 8-month Special Enrollment Period.
Can I get Medicare and Medicaid at the same time if my income is low?
Yes. If your income is near or under about 135% of the Federal Poverty Level (roughly $21,546 for an individual in 2026), you may qualify for a Medicare Savings Program that pays your Part B premium, or full dual Medicare and Medicaid eligibility through your state's program, such as Medi-Cal in California or MassHealth in Massachusetts. Check the current federal poverty level and Medicaid income limits for your state and apply through your state Medicaid agency; enrollment is year-round with no deadline.
What is the deadline to decide between Original Medicare and Medicare Advantage?
You can pick either Original Medicare or Medicare Advantage at any point during your 7-month Initial Enrollment Period or during a valid Special Enrollment Period. If you choose Original Medicare and want a Medigap supplement, you get a one-time 6-month guaranteed-issue window starting the month you are both 65 and enrolled in Part B; after that, Medigap insurers in most states can medically underwrite you.
