Yes, you can stay on your spouse’s health insurance at 65 in most situations. If your spouse’s employer has 20 or more employees, federal law requires the group health plan to keep covering you on the same terms it offers younger spouses, and Medicare eligibility is not a reason the employer can drop you or charge you more. The harder questions are whether to enroll in Medicare Part A anyway, whether to delay Part B, and how to handle the enrollment paperwork so you don’t trigger permanent penalties down the road.
The 20-Employee Rule Decides Your Rights
Employer size is the pivot. Under the Medicare Secondary Payer rules, employers with 20 or more full-time or part-time employees must continue offering the same group health coverage to Medicare-eligible spouses that they offer to everyone else. The employer plan pays first and Medicare pays second. The employer cannot drop you, raise your rate, or make Medicare enrollment a condition of staying.1Medicare. Who Pays First
If the employer has fewer than 20 employees, the arrangement flips. Medicare becomes the primary payer, the employer plan pays second, and small employers are not required to keep covering Medicare-eligible spouses at all. Some stop.2Centers for Medicare & Medicaid Services. Medicare Secondary Payer Manual
Multi-employer plans, like union health funds, work by their own logic. If even one participating employer in the plan has 20 or more employees, the MSP rules apply to the entire plan, including workers at smaller participating employers. Multi-employer plans can request an exemption for employees of specific small employers, so ask the plan administrator directly if this describes your situation.
Should You Enroll in Part A Anyway
Most people qualify for premium-free Part A based on their own or a spouse’s work history. If you’ve earned at least 40 Social Security credits (roughly 10 years of work), Part A costs you nothing.3Medicare. Working Past 65 Signing up for Part A alongside the employer plan gives you a secondary payer for hospital stays with no monthly premium attached, so for many people it’s a straightforward yes.
Part B is the one you can usually skip. As long as you’re covered under a group health plan based on your spouse’s current employment, you can delay Part B without penalty. That saves you the standard Part B premium, which is $202.90 per month in 2026.4Centers for Medicare & Medicaid Services. 2026 Medicare Parts A and B Premiums and Deductibles
If you don’t qualify for premium-free Part A, the 2026 Part A premium can run up to $565 per month. In that case, delaying both Part A and Part B and relying on the employer plan usually makes more sense, provided the employer plan qualifies as creditable coverage for drug purposes (more on that below).
One timing detail matters if you’re already collecting Social Security when you turn 65: Part A enrollment is automatic. You don’t get to opt out. That triggers a real problem for HSA contributors.5Social Security Administration. Medicare
The HSA Trap
If you’re on your spouse’s high-deductible health plan and contributing to a Health Savings Account, enrolling in any part of Medicare, including premium-free Part A, ends your ability to contribute. Federal tax law sets your HSA contribution limit to zero for any month you have Medicare, and there are no exceptions.6Office of the Law Revision Counsel. 26 US Code 223 – Health Savings Accounts
That is real money. The 2026 HSA contribution limits are $4,400 for self-only coverage and $8,750 for family coverage.7Internal Revenue Service. IRS Notice 2026-05
The trap deepens if you enroll in premium-free Part A after 65. Coverage is retroactive up to six months (though never earlier than the month you turned 65). Those retroactive months reduce your allowable HSA contributions for the year, and contributions you already made can become excess contributions. If that happens, withdraw the excess before your tax filing deadline (including extensions) to avoid a 6% excise tax.8Medicare. When Does Medicare Coverage Start
The practical rule: if HSA contributions are part of your financial plan, don’t enroll in any part of Medicare, including Part A, until you’re ready to stop contributing. And if you’re already drawing Social Security, plan on HSA contributions ending at 65 because Part A comes automatically.
Delaying Part D and Creditable Coverage
If you stay on the employer plan and delay Part D, the prescription drug benefit under that employer plan has to meet Medicare’s creditable coverage standard, meaning it’s at least as good as a standard Part D plan in actuarial value. If it is, you can delay Part D without penalty. If it isn’t, every month of delay adds to a permanent Part D late enrollment penalty.9Centers for Medicare & Medicaid Services. Final CY 2026 Part D Redesign Program Instructions
Employers must send a written notice to Medicare-eligible plan members each year before October 15 stating whether the drug coverage is creditable.10Centers for Medicare & Medicaid Services. Creditable Coverage Keep every notice. You’ll need them to prove creditable coverage later. If a notice doesn’t arrive, ask the employer directly. Not knowing your coverage was non-creditable won’t excuse the penalty.
The Part D penalty is 1% of the national base beneficiary premium ($38.99 in 2026) for every month you went without creditable drug coverage after first becoming eligible, and it lasts as long as you have Part D.11Centers for Medicare & Medicaid Services. The Part D Late Enrollment Penalty The Part B late penalty works the same way in spirit: 10% added to your monthly premium for every full 12 months you were eligible but not enrolled and not covered by employment-based insurance. It also lasts for life.12Medicare. Avoid Late Enrollment Penalties
When the Employer Coverage Ends
Staying on the spouse’s plan is a good answer until it isn’t. When your spouse retires, changes jobs, or the employer drops spousal coverage, you get an eight-month Special Enrollment Period to sign up for Part B (and Part A, if you delayed it). The eight months start when the employment ends or the coverage ends, whichever comes first, not when you decide to enroll.13Social Security Administration. Special Enrollment Period
This is the piece people miss. Only coverage based on current employment protects the SEP. Retiree coverage doesn’t count. COBRA doesn’t count either.
Why COBRA Is Not a Medicare Bridge
COBRA lets you continue the same employer plan temporarily by paying the full cost yourself, up to 102% of the plan’s total premium (employer and employee share plus a 2% administrative fee). That regularly runs $600 to $2,000 or more per month.14U.S. Department of Labor. FAQs on COBRA Continuation Health Coverage for Workers The standard COBRA period is 18 months, with extensions up to 29 months for disability or 36 months for events like a spouse’s death or divorce.15U.S. Department of Labor. COBRA Continuation Coverage
The trap: because COBRA is not considered coverage based on current employment, your eight-month SEP starts when the job ends, not when COBRA runs out. Elect COBRA and wait 18 months to enroll in Medicare, and you’ve blown past the SEP by ten months. You’ll wait for the General Enrollment Period (January 1 through March 31, coverage starting the following month) and carry a Part B late penalty for life.13Social Security Administration. Special Enrollment Period16Social Security Administration. When to Sign Up for Medicare
COBRA can still work as a short-term bridge during the weeks it takes Medicare to activate, as long as you sign up for Medicare inside the SEP. Just don’t treat it as a substitute for enrollment.
Paperwork to Keep Now
The document that makes the SEP work is Form CMS-L564. Your spouse’s employer completes it to confirm the dates you were covered under the group plan and the dates of employment. Without it, you can’t prove SEP eligibility, and you’re back to penalties.17Centers for Medicare & Medicaid Services. Form CMS-L564 Request for Employment Information
Ask for it before your spouse leaves the job. Former employers can be slow, and burning weeks of an eight-month window waiting for a signed form is avoidable. Along with the CMS-L564, hang onto pay stubs or benefits statements showing active plan participation, plus every annual creditable coverage notice from the drug plan. Some employers also ask for a marriage certificate to confirm eligibility, and some want a written attestation or Part B waiver before letting you remain on the group plan as a Medicare-eligible spouse. Those are your protection against a penalty fight later.