If you are turning 65 and plan to keep your job, “working at 65 and Medicare” do not always go together. What you decide in these months can save you from lifetime penalties or, the other way around, cost you taxes for contributing to a health savings account (HSA) when you no longer should. This guide walks you through, step by step and with official sources, how to coordinate Medicare with your job coverage without slipping up.
Do you have to enroll in Medicare if you keep working?
The answer depends on your employer’s size. Medicare’s coordination of benefits rule works like this:
- 20 or more employees: the employer health plan pays first and Medicare pays second. Here it often makes sense to delay Part B and keep your job coverage while you have it.
- Fewer than 20 employees: Medicare pays first and the employer plan pays second. In this case you almost always want to enroll in Part A and Part B at 65, because the job plan assumes you already have Medicare.
Before you decide, ask Human Resources how your plan treats people with Medicare. A wrong answer can leave you without primary coverage right when you need it most.
“Free” Part A and the HSA trap
Most people pay no premium for Part A (hospital coverage) because they already paid enough Medicare taxes during their working years. That is why many think there is “nothing to lose” by turning it on at 65. But there is an important trap if you contribute to an HSA.
The IRS is clear: once you are enrolled in any part of Medicare, including Part A, your HSA contribution limit drops to zero. According to IRS Publication 969 (tax year 2025): “Beginning with the first month you are enrolled in Medicare, your contribution limit is zero.”
The most dangerous detail is retroactive enrollment. When you sign up for Part A after your eligibility date, Medicare can backdate your coverage up to 6 months (but not before you turned 65). Those HSA contributions you made during those retroactive months become excess contributions. The IRS itself states that if your enrollment is backdated, “any contributions to your HSA made during the period of retroactive coverage are considered excess.” Excess contributions can trigger a 6% excise tax.
So if you plan to keep contributing to your HSA, it is wise to stop contributing at least 6 months before you enroll in Medicare or claim Social Security (which turns on Part A automatically).
This is not tax advice; talk to a tax professional about your situation.
How to avoid the lifetime Part B penalty
Part B (medical coverage) does have a monthly premium and does carry a penalty if you enroll late without valid coverage. The good news: if you have employer coverage based on current employment (yours or your spouse’s), you can delay Part B without a penalty.
When you stop working or lose that job coverage, an 8-month Special Enrollment Period (SEP) opens to sign up for Part B with no penalty. Heads up: the SEP starts when employment or coverage ends, not when COBRA runs out. If you only keep COBRA and let the 8 months pass, you can end up with a penalty and a gap in coverage.
Coordinating coverage: who pays first
Having two plans does not mean paying twice; it means one pays first and the other pays after. Reviewing the employer-size rule:
- Employer with 20+ employees: the job plan is the primary payer; Medicare is secondary.
- Employer with fewer than 20: Medicare is primary; the job plan is secondary.
Knowing who pays first prevents denied claims and surprise bills. If your plan is secondary and you have not activated Part B, you can be left with no primary payer for those services.
Talk to a bilingual agent
Coordinating Medicare with your job coverage, protecting your HSA, and not missing the 8-month SEP are decisions with strict deadlines. A licensed agent can review your situation and help you enroll on time, in English or Spanish.
Talk to a bilingual Medicare agent and review your options here.
You may also find this useful: How to help your parents enroll in Medicare in 2026 and Medicare Part D: the \$2,000 (\$2,100) cap in 2026.
Official sources: Medicare.gov, “Working past 65” and IRS, Publication 969 (HSA).
Frequently asked questions
Can I delay Medicare if I keep working?
Yes, if your employer has 20 or more employees and your coverage is based on current employment, you can delay Part B (and sometimes Part A) without penalty while you keep that coverage. If the employer has fewer than 20 employees, you usually must enroll at 65 because Medicare pays first.
Is it worth taking only Part A?
Part A is usually premium-free, so many people turn it on. But if you contribute to an HSA, enrolling in Part A sets your contribution limit to zero from that month. If you want to keep contributing, you may prefer not to take even Part A yet.
Can I keep contributing to my HSA with Medicare?
No. The IRS sets your contribution limit to zero from the first month you are enrolled in Medicare, including Part A. Because Part A can be backdated up to 6 months, it is wise to stop contributing at least 6 months before you enroll. Check with a tax professional.
Will I owe a late Part B penalty?
No, if you had employer coverage based on current employment. When that job ends you get an 8-month Special Enrollment Period to take Part B without penalty. If you let that window pass, a lifetime penalty can apply.
Which insurance pays first?
It depends on the employer’s size. With 20 or more employees, the job plan pays first and Medicare second. With fewer than 20, Medicare pays first and the job plan pays second.
When is my special enrollment period when I retire?
Your Special Enrollment Period lasts 8 months and begins when your job or job-based coverage ends, whichever comes first. COBRA does not extend that window, so it is best to act early so you do not go without coverage.
