Turning 65 while you still work for a large employer is the one Medicare situation where waiting is usually the smart move. Federal Medicare Secondary Payer rules treat an employer with 20 or more employees as the primary payer for active workers 65 and older, so your group plan pays first and Medicare would pay second. Enrolling in Part B at $202.90 per month in 2026 would often duplicate coverage you already have through payroll. The catch is that the delay is only penalty-free when every condition is met: the coverage must come from current employment (yours or your spouse's), the employer must meet the 20-employee threshold, and you must enroll within 8 months after the job or the group coverage ends. Medicare eligibility starts at 65 regardless of employment, so the decision is about timing and paperwork, not about whether you qualify. In 2026, a mistake on any condition produces a Part B penalty of 10% for each full 12-month period you went without it, charged every month for the rest of your life.
Three pieces of the puzzle trip up most workers at 65: Part A, Part D, and the Health Savings Account. Medicare Part A is premium-free for anyone with 40 quarters of Medicare-covered work, and enrolling carries no penalty, but Part A enrollment stops HSA contributions and can reach back 6 months. Part D drug coverage follows a separate 63-day creditable-coverage rule, so the annual notice from your employer matters in 2026. Finally, the delay only works if you collect proof when it is time to enroll: Form CMS-L564 from your employer plus Form CMS-40B from you. This guide walks through the six steps, the documents, the pitfalls with COBRA and retiree plans, and the Medicaid and Medicare Savings Program pivot for workers whose income falls below the 2026 limits. Check Medicare eligibility and the Federal Poverty Level pages for the income lines that decide help with premiums.
6 Steps to Get Coverage
Common Mistakes That Cost People Thousands
Large-employer workers at 65 lose the most money on the same handful of errors in 2026, and most of the resulting penalties are permanent:
- Treating COBRA or a retiree plan as active coverage. Neither counts for the Part B delay, so the 8-month SEP clock still runs from the day your job ends.
- Assuming the employer has 20 employees without asking. Employers below that threshold make Medicare the primary payer at 65, and the group plan may refuse claims Medicare should have paid.
- Enrolling in Part A without stopping HSA contributions. Part A can reach back 6 months, so contributions made in that period create a 2026 tax penalty of 6% on the excess.
- Ignoring the creditable drug coverage notice. In 2026, a 63-day gap without creditable Part D coverage triggers a 1% per month penalty on the national base premium for life.
- Waiting to ask for Form CMS-L564 until after retirement. Employers can take weeks to complete it, and a delayed form postpones the SEP application.
What Counts as Active Employer Coverage for the Part B Delay in 2026
Active employer coverage means a group health plan offered because you, or your spouse, currently work for an employer with 20 or more employees. Federal Medicare Secondary Payer rules under Section 1862(b) of the Social Security Act make that plan primary and Medicare secondary, which is why delaying Part B causes no penalty. Several look-alike arrangements fail the test. COBRA continuation coverage fails it, even though the plan and network look unchanged, because you are no longer a current employee. Retiree health plans fail it. An individual plan bought on healthcare.gov fails it, and a Marketplace plan can also expose you to repayment of premium tax credits reported on Form 1095-A once Part A starts. VA benefits and Tricare are separate rules, so confirm with the agency before you rely on them. Employer headcount matters too: a company with 15 employees is below the threshold in 2026, and Medicare becomes primary at 65. Ask HR for the employee count in writing and keep it with your benefits papers. If the answer is borderline, enroll in Part B on time, because a few months of duplicate premium at $202.90 in 2026 costs far less than a lifetime penalty.
Part A, Your HSA, and the 6-Month Lookback in 2026
Health Savings Account holders face a rule that surprises even careful planners. Medicare Part A starts retroactively up to 6 months when you apply after age 65, but never earlier than the month you turned 65. Federal tax law bars HSA contributions in any month you are covered by Medicare, so contributions during that retroactive window become excess contributions. For 2026, the HSA limit is $4,400 for self-only coverage and $8,750 for family coverage, plus a $1,000 catch-up at age 55 and older, and the excess is taxed at 6% per year until corrected. Claiming Social Security retirement benefits has the same effect, since it triggers automatic Part A enrollment. The safe approach is to stop HSA contributions at least 6 months before you apply for Part A or Social Security, then keep spending the existing HSA balance tax-free on qualified medical costs, including Medicare premiums. If you do not contribute to an HSA, enrolling in premium-free Part A at 65 is usually wise, because Part A then covers hospital stays as secondary protection behind the employer plan at no premium cost in 2026.
Why Form CMS-L564 and Form CMS-40B Decide Your Part B Special Enrollment Period in 2026
Social Security grants the 8-month Part B Special Enrollment Period only after it sees proof of current employment and group coverage. Form CMS-L564, the Request for Employment Information, is the employer's statement that you were covered under an active group plan, with the dates it started and ended. Form CMS-40B is your own application for Part B. Social Security reads the two forms together, so a missing employer signature or a gap in dates stalls the claim and can push your Part B start date later than planned. Ask your payroll or benefits office to complete Form CMS-L564 before your last day, while the person who knows your coverage dates is still reachable. If you enroll in Part B while still working, Social Security may accept your own attestation, but keep the same documents ready. Online submission through your my Social Security account at ssa.gov is the fastest route in 2026. Part B then starts the month after your application is approved, so submit the forms in the month your group coverage ends to avoid a gap.
Medicaid and Medicare Savings Program Help for Workers at 65 in 2026
Workers at 65 with modest wages sometimes qualify for help they never knew existed. Medicare Savings Programs, run by state Medicaid agencies, can pay the $202.90 Part B premium in 2026 when income falls near or below roughly 135% of the Federal Poverty Level, with income limits that vary by state. State agencies operate under local names: Medi-Cal in California, MassHealth in Massachusetts, AHCCCS in Arizona, and BadgerCare in Wisconsin. Because Medicaid enrollment is year-round per medicaid.gov, you can apply the month you become eligible, with no enrollment deadline. Qualifying for a Medicare Savings Program also changes the Part B delay calculation: if the state pays your premium in 2026, enrolling in Part B costs you nothing out of pocket, and the penalty risk disappears from the decision. Check the Medicaid income limits and Federal Poverty Level pages for 2026 household thresholds, then call your state Medicaid agency for the exact screening rules. Extra Help can also cap Part D costs at a few dollars per prescription in 2026 for the same income group.
Frequently Asked Questions
What is the Part B window if I am still working at 65 with large-employer coverage?
Your Initial Enrollment Period is 7 months, from 3 months before to 3 months after your 65th birthday month. If you turn 65 on August 15, 2026, it runs May 1, 2026 through November 30, 2026. Active group coverage from an employer with 20 or more employees lets you skip Part B during that window with no penalty. The 8-month Special Enrollment Period then starts the month after your job or group coverage ends, whichever comes first. If coverage ends December 31, 2026, you can enroll from January 1, 2027 through August 31, 2027. Part B costs $202.90 per month in 2026, so delaying saves real money while you remain covered.
How do I document my employer coverage when I enroll in Part B?
Two forms document the delay. Form CMS-L564 (Request for Employment Information) is completed and signed by your employer or plan administrator, confirming the dates of your active group coverage. Form CMS-40B (Application for Enrollment in Medicare Part B) is your own request. Submit both to Social Security through your my Social Security account at ssa.gov, by fax or mail, or at a local office. Gather your Medicare card number if you have one, your Social Security number, and proof of your employment end date. Request Form CMS-L564 from HR before your last workday in 2026, because employers can take weeks to return it.
What happens if I miss the 8-month Part B Special Enrollment Period?
Missing the 8-month SEP leaves only the General Enrollment Period, which runs January 1 through March 31 each year, with coverage starting the month after you sign up. You also pay a 2026 Part B late penalty of 10% of the standard premium for every full 12 months you could have had Part B but did not. With the 2026 premium of $202.90, two full years late adds about $40.58 per month in 2026, and the surcharge lasts for life. A gap in coverage is also possible, because the employer plan may already be gone. Count the 8 months from the first day after your coverage or employment ends and submit early.
Can I get retroactive coverage when I enroll in Medicare after 65?
Part A can be retroactive up to 6 months, but never earlier than the month you turned 65, when you apply after your Initial Enrollment Period. Part B under the employer SEP generally starts the month after you enroll, so Part B has no retroactive benefit in 2026. Plan your sign-up before the group coverage ends so the two overlap. Retroactive Part A creates one hazard: it counts as Medicare coverage for those months, which blocks HSA contributions and can turn contributions into taxable excess. Ask Social Security to confirm your Part A start date in writing at ssa.gov or 1-800-772-1213.
What is the difference between COBRA and Medicare Part B when my large-employer job ends?
In 2026, COBRA continues your employer plan at up to 102% of the full premium, but COBRA does not count as active employer coverage for the Part B delay. The 8-month SEP clock starts when your job or group coverage ends, even if you elect COBRA for 18 months. Enroll in Part B within those 8 months, because Medicare generally becomes primary and COBRA secondary, and COBRA can end once you are entitled to Medicare. In 2026 individual COBRA often costs $400 to $900 per month against $202.90 for Part B, so most people drop COBRA in favor of Part B plus Medigap or Part D.
Does enrolling in Medicare affect my Health Savings Account?
Enrolling in any part of Medicare, including premium-free Part A, ends your eligibility to contribute to an HSA. Part A can start up to 6 months retroactively, so stop contributions 6 months before you apply. Contribution limits for 2026 are $4,400 for self-only coverage and $8,750 for family coverage, with a $1,000 catch-up at 55 and older. Excess contributions face a 6% excise tax each year in 2026 until fixed. You keep the existing balance and can spend it tax-free on qualified expenses, including Medicare premiums. If you want to keep funding an HSA, delaying both Part A and Part B is possible only if you do not claim Social Security.
Do I need Part D if my large-employer plan covers prescriptions?
Part D is optional while your employer drug coverage is creditable, meaning it pays at least as much as standard Medicare drug coverage. Your employer must send an annual Notice of Creditable Coverage, so keep it. If the employer coverage ends, you have 2 months to join a Part D plan through a Special Enrollment Period, and you must not go 63 days or more without creditable coverage. A longer gap adds a 1% per month penalty on the national base premium for life in 2026 and beyond. Compare plans on medicare.gov before the Medicare Annual Election Period, October 15 through December 7, 2026, for 2027 coverage.
Do I qualify for Medicaid or a Medicare Savings Program to help pay Part B in 2026?
Medicare Savings Programs can pay your $202.90 Part B premium in 2026 when your income is near or below roughly 135% of the Federal Poverty Level, with state-specific limits and, in some states, asset tests. Medicaid itself is year-round per medicaid.gov, so no deadline applies. State brands include Medi-Cal in California, MassHealth in Massachusetts, AHCCCS in Arizona, and BadgerCare in Wisconsin. Working at 65 does not disqualify you, because the programs look at countable income. Apply through your state Medicaid agency, and ask for the Qualified Medicare Beneficiary, Specified Low-Income Medicare Beneficiary, and Qualifying Individual categories by name.
