Medicare While Still Working Master Guide

What Medicare While Still Working Actually Requires

Medicare while still working is not a single decision but four: whether to take Part A at 65, whether to delay Part B, what to do about Part D, and what happens to a health savings account. The answers depend on the employer’s size, whether the coverage is the worker’s own or a spouse’s, and whether the worker is contributing to an HSA. Get them right and the worker keeps the job plan without penalty; get one wrong and the penalty lasts for life.

The stakes are concrete. Part B costs $202.90 a month in 2026, so delaying it while a good group plan is primary saves real money. But the late enrollment penalty is 10 percent of the premium for every full 12 months of delay without qualifying coverage, added forever. The working past 65 guide gives the plain answer to whether a worker has to sign up; this page gives the rules behind it and links the guide for each.

The 20-Employee Rule

An employer with 20 or more employees must offer a worker over 65 the same coverage as younger workers, and that group plan pays first. Medicare, if the worker has it, pays second. A worker in that situation can decline Part B at 65, keep the group plan, and enroll later with no penalty, because coverage under a plan based on current employment is the exception the penalty rule carves out. The 20-employee rule guide covers how the count is made and what happens when the employer crosses the line.

Under 20 employees, the order flips. Medicare is primary, and the group plan pays only what Medicare would have left — and a plan that assumes the worker has Medicare will pay as if Medicare paid first whether or not it did. A worker who declines Part B in that situation is uninsured for the Medicare share, faces the penalty later, and often does not find out until a hospital bill arrives. The small-employer gap guide is the warning.

The count that governs medicare while still working is the employer’s, not the plan’s, and multi-employer plans and related companies have their own rules. A worker who is not certain should ask the benefits office in writing whether the plan is primary or secondary to Medicare for an active employee over 65. The answer decides everything about medicare while still working.

Part A: Free, Unless There Is an HSA

Part A is premium-free for nearly everyone with 40 quarters of work, and most workers take it at 65 as a secondary hospital payer. The exception is the worker contributing to a health savings account. Federal tax rules bar HSA contributions for any month a person is enrolled in any part of Medicare, and Part A enrollment is backdated up to six months from the application date. Contributions in those months become excess contributions with a tax penalty.

The Part A while working guide covers the decision, and the HSA six-month lookback guide covers the trap: a worker who applies for Part A or for Social Security — which enrolls in Part A automatically — must stop HSA contributions six months before the application month. A worker who wants to keep contributing declines Part A too, which is allowed only if Social Security benefits are not being drawn.

The employer’s contribution to the HSA is caught by the same rule. A worker who cannot stop the employer’s deposit should ask for the equivalent as taxable pay for the months in question. The IRS penalty is small per year but it repeats until the excess is withdrawn.

Part B: How to Delay It Correctly

Delaying Part B is a choice the worker makes by not enrolling, but it has to be recorded correctly or Social Security assumes the worker wants it. A person already drawing Social Security is enrolled in Part B automatically at 65 and must send back the card to decline. A person not yet drawing benefits simply does not apply. The delay Part B guide covers the forms, the proof of employer coverage to keep, and the timing.

The proof is the piece people lose when handling medicare while still working. When the worker later enrolls under the special enrollment period, Social Security asks for Form CMS-L564, completed by the employer, showing the months of group coverage based on current employment. An employer that has since closed, been acquired, or lost its records makes that form hard to get, so a worker should have it signed and filed away while the employer is still there.

Medicare while still working means Part B is optional only for the worker with a primary group plan from an employer of 20 or more. For everyone else — small employer, COBRA, retiree plan, the marketplace, a spouse’s plan from a small employer — Part B at 65 is not optional, and the penalty for treating it as optional is permanent.

The 8-Month Special Enrollment Period

When the job ends or the group coverage ends, whichever comes first, an 8-month special enrollment period opens for Part B. Enrolling within it means no penalty and coverage starting the month after enrollment, or the first of the following month if the worker chooses. The special enrollment period guide covers the exact count and the forms — CMS-40B for the worker and CMS-L564 for the employer.

The window is the part of medicare while still working that is shorter than it looks. Coverage should start the month the group plan ends, which means applying in the last month or two of work, not the last month of the window. And the Part D window is different: a worker leaving creditable drug coverage has 63 days to join a Part D plan, not 8 months, before the Part D penalty starts. The retirement checklist puts both on one calendar around the last day of work.

A worker who misses the 8 months waits for the general enrollment period, January through March, with coverage starting the month after enrollment, and pays the penalty for the months missed. There is no hardship exception for not knowing.

COBRA, Retiree Coverage and the Spouse’s Plan

COBRA is the trap with the highest penalty count. It is group coverage, it is often good coverage, and it does not count as coverage based on current employment. A worker who leaves at 66, takes 18 months of COBRA, and enrolls in Part B afterward has missed the 8-month window by ten months, pays the penalty for life, and may have been uninsured for the Medicare share the whole time, because COBRA plans pay secondary to Medicare whether or not Medicare was taken. The COBRA and Medicare guide covers the trap in full.

Retiree health coverage works the same way: it pays secondary to Medicare and does not delay the Part B clock. The retiree coverage guide covers which one pays first and what a retiree plan is actually worth once Medicare is primary.

A spouse’s employer plan does count, if the spouse is actively employed and the employer has 20 or more employees. A 65-year-old on a working spouse’s large-employer plan can delay Part B and use the special enrollment period when the spouse’s employment ends. The spouse’s employer plan guide covers the count and the forms, which come from the spouse’s employer.

Part D and the Creditable Coverage Letter

Part D has its own penalty — one percent of the national base premium for every month without creditable drug coverage after the initial enrollment period, for life — and its own exception. Drug coverage that is at least as good as standard Part D is creditable, and a worker with creditable coverage through the job can delay Part D without penalty. Most large-employer plans are creditable; many high-deductible plans are not.

The employer must tell the worker each year whether the plan’s drug coverage is creditable, in a written notice, and that notice is what the worker will need when enrolling in Part D later. The creditable coverage letter guide covers what it says, when it arrives, and what to do if the plan is not creditable. The letter should be filed with the CMS-L564, because both are asked for at the same time.

Medicare while still working means checking the letter every year, because a plan that was creditable last year can stop being creditable this year, and the penalty clock starts the month it does.

Veterans and TRICARE

VA health care is not creditable coverage for Part B purposes and does not delay the penalty clock; a veteran who relies on the VA and declines Part B at 65 pays the penalty if Part B is taken later. VA drug coverage is creditable for Part D, so the Part D penalty does not apply. The veterans and Part B guide and the VA prescriptions and Part D guide cover the two rules and why they differ.

TRICARE For Life is the opposite: it requires Part B. A military retiree who reaches 65 and does not enroll in Part B loses TRICARE coverage entirely. The TRICARE For Life guide explains why Part B is not optional there, and the VA and Medicare together guide covers how a veteran uses both systems.

Mistakes That Create a Lifetime Penalty With Medicare While Still Working

The first mistake is delaying Part B at a small employer. The second is treating COBRA or a retiree plan as current employment. The third is contributing to an HSA after applying for Social Security, which enrolls in Part A automatically and backdates six months. The fourth is losing the employer’s signature on the CMS-L564 by waiting until the employer is gone.

The fifth is missing the 63-day Part D window inside the 8-month Part B window. The sixth is assuming VA coverage delays the Part B clock. The seventh is enrolling in Part B at the end of the special enrollment period instead of the beginning, leaving a gap between the group plan ending and Medicare starting.

The last is not asking the benefits office, in writing, whether the plan is primary to Medicare for an active worker over 65. Every rule about medicare while still working turns on that answer, and the answer is the employer’s to give.

The Enrollment Periods, Named

Medicare while still working means knowing which window is which. The initial enrollment period is the seven months around the 65th birthday, and the turning 65 checklist and the complete enrollment checklist walk it month by month. The special enrollment period guide lists every event that opens a window later, of which leaving employer coverage is the largest. The missed enrollment guide covers what happens when neither was used, and the late enrollment penalty guide gives the arithmetic.

The when to sign up guide and the complete enrollment guide put the whole calendar in one place, and the must-sign-up-at-65 myth guide corrects the assumption that sends healthy workers into Part B they did not need. The Medigap open enrollment guide covers the six-month guaranteed-issue window that opens when Part B starts — which for a worker who delayed Part B opens at 68 or 70, not 65, and is the reason delaying Part B costs nothing on the Medigap side either.

Two special cases of medicare while still working have their own guides. The self-employed guide covers the worker with no employer plan, for whom none of the delay rules apply. And the going back to work guide covers the retiree who took Part B, returned to a large employer, and wants to drop it — which is allowed, and reopens the special enrollment period later.

Coordination in Practice: Who Pays What, and the Cost Side

Once the worker has both, medicare while still working becomes a coordination question, and the coordinating Medicare and employer insurance guide explains the order of payment in each case. The employer creditable coverage guide and the what creditable coverage means guide cover the Part D side in more depth, and the Part D guide explains what the worker is delaying. The COBRA vs Medicare guide and the retiree insurance coordination guide are the second reads on the two traps above.

The cost side is why the medicare while still working decision matters. The Part B premium guide gives the 2026 figure and what moves it, the IRMAA guide explains why a worker with a high salary pays more for Part B than a retiree, and the income change guide covers the year after retirement, when the surcharge is based on a working year’s income and can be appealed. The premium deduction guide covers how the premium is collected once the worker draws Social Security.

The Medicare and HSA rules guide is the longer read on the tax side, and the premium tax deduction guide covers what the worker can write off once premiums start. The spouse’s employer coverage enrollment guide is the companion to the spouse section above, and the TRICARE to Medicare guide and the Medicare and VA benefits guide cover the military transition in more detail.

When to Get Help

Most workers handle medicare while still working with the guides on this page, a written answer from the benefits office, and a SHIP counselor. Two situations call for more. A worker with an HSA who has already applied for Social Security, where a tax professional has to unwind the excess contributions. And a worker who already missed a window, where the penalty removal guide covers reconsideration and the equitable relief available when a federal employee gave wrong advice.

The retirement checklist is the tool for the last 60 days of work. Whichever route, keep the creditable coverage letters and the signed CMS-L564 in one folder from age 64 on, because both are asked for years later, by an agency that cannot get them for you.

Medicare While Still Working: Frequently Asked Questions

Do I have to sign up for Medicare at 65 if I am still working?

Part A, usually yes, unless you are contributing to an HSA. Part B, only if your employer has fewer than 20 employees or your coverage is COBRA, retiree, marketplace, or VA. With a primary group plan from a large employer, Part B can wait without penalty.

What is the Part B late enrollment penalty?

Ten percent of the Part B premium — $202.90 a month in 2026 — for every full 12-month period you could have had Part B but did not, added to the premium for as long as you have Medicare. Months covered by a primary group plan based on current employment do not count.

Can I keep contributing to my HSA?

Not for any month you are enrolled in any part of Medicare, and Part A backdates up to six months from the application. Stop contributions six months before applying for Part A or Social Security, and decline Part A if you want to keep contributing — which is allowed only if you are not drawing benefits.

Does COBRA count as employer coverage for medicare while still working?

No. COBRA is group coverage but it is not based on current employment. It pays secondary to Medicare and does not delay the 8-month special enrollment period, which starts when the job ends, not when COBRA ends.

How long is the special enrollment period?

Eight months for Part B, starting the month after employment or the group coverage ends, whichever is first. Sixty-three days for Part D after creditable drug coverage ends. The two clocks are different lengths and start the same day.

I am on my wife’s plan. Do I need Part B?

If she is actively working and her employer has 20 or more employees, no — her plan is primary and you get the special enrollment period when her employment ends. If her employer is under 20, or she has retired, yes.

What forms do I need when I finally enroll?

CMS-40B, the Part B application, and CMS-L564, completed by the employer to prove the months of group coverage based on current employment. Get the L564 signed while the employer still exists, and keep every year’s creditable coverage letter for Part D.

The Last 60 Days of Work

This page is the rules. The retirement checklist is the calendar: what to do in the 60 days around the last day of work so Part B, Part D and the HSA all land without a gap or a penalty.

Open the Retirement Checklist →

Sources & How to Verify

The rules on this page are drawn from the Medicare enrollment regulations, the Medicare Secondary Payer rules for working-aged beneficiaries, IRS Publication 969 on health savings accounts, and the 2026 Part B premium. Premiums and penalties change every year, so confirm the current figures at Medicare.gov and with your employer’s benefits office.

• Medicare.gov: www.medicare.gov/basics/get-started-with-medicare/sign-up/when-does-medicare-coverage-start – enrollment periods, the special enrollment period and the late enrollment penalties
• Social Security Administration: www.ssa.gov/medicare/sign-up – Part A and B enrollment and the employer form CMS-L564
• Internal Revenue Service: www.irs.gov/publications/p969 – Publication 969: health savings accounts and the Medicare rule
• Centers for Medicare & Medicaid Services: www.cms.gov/medicare/coordination-benefits-recovery/overview – the working-aged Medicare Secondary Payer rules and the 20-employee count

Content last reviewed September 2026. If you notice outdated information, please contact us.

Related Guides

In depth on this topic:

• Working Past 65 and Medicare — Do You Have to Sign Up?
• The 20-Employee Rule — Whether Your Job’s Plan Pays Before Medicare
• The Small-Employer Gap
• How to Delay Part B Correctly — Forms, Proof, and Timing
• Part B Special Enrollment Period — The 8-Month Window

The traps:

• COBRA and Medicare — The Trap That Creates a Lifetime Penalty
• Medicare and Your HSA — The 6-Month Lookback
• Should You Take Part A While Still Working?
• Creditable Coverage — The Letter That Saves You From the Part D Penalty
• Retiree Health Coverage and Medicare — Which One Pays First
• On a Spouse’s Employer Plan at 65

Veterans and retirement:

• Do Veterans Need Medicare Part B?
• VA Prescriptions and Part D
• TRICARE For Life and Medicare — Why Part B Is Not Optional
• Retiring After 65 — A Medicare Checklist
• How to Get a Medicare Penalty Removed

The enrollment periods:

• Medicare Initial Enrollment Period — Your 7-Month Window
• Medicare Special Enrollment Periods — All Qualifying Events
• Medicare Late Enrollment Penalty — Part B and Part D
• What Happens If You Miss Your Initial Enrollment Period
• Medigap Open Enrollment Period
• Turning 65 Medicare Checklist
• Myth: You Must Sign Up for Medicare at 65

Coordination and cost:

• Coordinating Medicare with Employer Insurance
• Is Your Employer Coverage Creditable for Medicare
• COBRA vs Medicare
• Retiree Insurance and Medicare
• Medicare Part B Premium 2026
• Complete Guide to IRMAA
• Medicare and HSA Rules
• Self-Employed and Turning 65
• Going Back to Work After Starting Medicare

• Medicare and Employer Coverage
• Medicare Enrollment

Informational only — not legal, tax or financial advice. Medicare Cover Guide is an independent educational resource, not a government agency, an insurer, or a law firm. Rules, deadlines and figures change by legislation and vary by state. For your specific situation, contact your state SHIP counselor, the office named in your state guide, or a licensed attorney in your state.