Educational only. I am not an actuary, attorney, licensed insurer, or Medicare counselor. This article restates Medicare.gov, CMS, and SSA rules on working past 65. Ask your employer benefits office how your group plan coordinates with Medicare, then enroll through Social Security. Official sites: Medicare.gov, SSA.gov. SHIP counseling: shiphelp.org.
The rule that decides the delay
Do not delay Part B unless your coverage is group health plan coverage based on you or your spouse’s current employment as Medicare defines it. If it is, you can often wait without a Part B late enrollment penalty and use an 8-month Special Enrollment Period (SEP) when employment or that coverage ends, whichever happens first. If the coverage is COBRA, retiree insurance, Marketplace coverage, or a stipend plan that is not a group health plan, waiting can create a permanent premium penalty and a coverage gap.
After 18 years in lead generation around insurance and health, I see the same mistake: people treat any “job-related” insurance as permission to skip Part B. Medicare.gov and CMS draw the line at current employment.
Premium-free Part A vs Part B timing
Medicare.gov’s working-past-65 page: if you do not have to pay a premium for Part A, you can sign up at 65 or anytime later. Most people qualify for premium-free Part A through their own or a spouse’s work history (generally 40 quarters). Those who must buy Part A face 2026 premiums of $311 (30-39 quarters) or $565 (fewer than 30 quarters), per CMS.
Part B is the premium almost everyone pays. The 2026 standard Part B premium is $202.90. Late enrollment generally adds 10% for each full 12-month period you could have had Part B but did not, usually for as long as you keep Part B. The working-past-65 exception exists to avoid that penalty when group coverage based on current work continues.
What “current employment” means
CMS’s employer-partner guidance and SSA’s SEP help page align:
- You (or your spouse) are still working, and
- You have coverage under an employer or union group health plan based on that current employment.
While that is true, you may enroll in Part B anytime without the late penalty. After employment ends or the group coverage based on that employment ends (whichever is first), you get up to 8 months to sign up. Medicare.gov: the SEP starts when you stop working or lose the insurance, even if you choose COBRA or other coverage that is not Medicare.
COBRA and retiree health plans are not coverage based on current employment. CMS and Medicare.gov both say you are not eligible for this SEP when that coverage ends. Marketplace coverage and many stipend arrangements likewise do not create this SEP. Ask whether the plan is employer group health plan coverage as the IRS defines it. If it is not, sign up for Medicare when you first become eligible.
Employer size and who pays first
Even when you qualify to delay Part B, the employer’s size affects whether delaying is practical.
Medicare.gov’s coordination rules: if you are 65 or older and have group coverage based on current employment, and the employer has 20 or more employees (or is in a multi-employer plan where at least one employer has 20 or more), the group plan usually pays first and Medicare pays second. If the employer has fewer than 20 employees, Medicare usually pays first. Small-employer plans may pay little or nothing if you do not have Part A and Part B. Ask the benefits administrator in writing before you skip Part B at a small firm.
Disability-based Medicare uses a 100-employee large-group threshold when coverage is based on a family member’s work. ESRD has separate coordination rules. Those paths are outside this article’s main age-65 worker focus.
How the 8-month SEP works in practice
Medicare.gov “when does Medicare coverage start” and the Enrolling in Medicare Part A & Part B booklet:
- You can sign up anytime while covered by the group plan based on current work, or during the 8 months after employment or that coverage ends, whichever ends first.
- Coverage generally begins the month after Social Security gets your completed request.
- If you sign up while still working, or within the first full month after employer coverage ends, you can ask to delay the Part B start date up to 3 months.
- This SEP does not apply if you are eligible based on ESRD, or if you are still inside your Initial Enrollment Period.
- Getting COBRA does not pause or restart the 8-month clock.
Forms typically include CMS-40B (Application for Enrollment in Part B) and CMS-L564 / CMS-L564A (Request for Employment Information) when you already have Part A. Sign up through SSA online or your local Social Security office. Railroad Retirement Board handles RRB annuitants.
Miss the 8 months and you usually wait for the General Enrollment Period (January 1 through March 31), with coverage starting later (often July 1 for that path), and you may owe the Part B late penalty.
COBRA and retiree coverage traps
Medicare.gov COBRA guidance for people who have not signed up for Medicare yet:
- Sign up for Medicare when you turn 65 to avoid gaps and a monthly Part B late penalty.
- COBRA will probably end once you sign up.
- Do not wait until COBRA ends to sign up for Part B. COBRA does not extend your limited time to sign up for Medicare.
If you already have Medicare and then take COBRA, COBRA generally pays after Medicare (with an ESRD exception noted on Medicare.gov).
Retiree coverage from a former employer is also not current employment. It may not pay during periods when you were eligible for Medicare but did not enroll. Ask whether you need both Part A and Part B for full retiree benefits, and whether joining a non-employer Advantage or drug plan will cancel coverage for you or dependents.
Drugs, creditable coverage, and HSAs
Prescription drug rules run on a parallel track. Medicare.gov: as long as you have creditable drug coverage, you can wait to join a Part D plan or an Advantage plan with drugs. Your plan must tell you whether coverage is creditable and usually sends that notice yearly. Keep it. You avoid the Part D late enrollment penalty if you do not go more than 63 days without creditable drug coverage.
If you have an HSA, Medicare.gov advises that you and your employer should stop HSA contributions 6 months before you retire or apply for Social Security (or RRB) benefits, to avoid a tax penalty. Confirm timing with your benefits office and tax advisor. Enrolling in Medicare Part A can affect HSA eligibility even when Part B is delayed.
Before you enroll or delay
- Ask HR whether coverage is based on current employment and how many employees the employer has for Medicare secondary-payer rules.
- Ask whether you need Part A, Part B, or both for the plan to pay correctly at 65.
- Ask whether drug coverage is creditable; keep the written notice.
- If coverage will end, sign up for Part B about a month before the end date so Social Security can process forms without a gap.
- After A and B start, choose Original Medicare (with or without Medigap and Part D) or Medicare Advantage. Check whether retiree coverage survives that choice.
Put simply
Working past 65 still means confirming whether your coverage is group health based on current employment. If yes, you may delay Part B without a late penalty and use an 8-month SEP when work or that coverage ends first. If the coverage is COBRA, retiree, or otherwise not current-employment group coverage, the SEP you think you have may not exist. Confirm with the employer, SSA, and Medicare.gov before you skip a premium that later becomes permanent.
