Medicare is not always the primary payer for your medical bills

Medicare pays second, not first, in several common situations. If you have group health insurance through an employer, that plan pays first — even if you are over 65 and enrolled in Medicare. If you are still working and your employer has 20 or more employees, your employer plan is primary. The same rule applies if your spouse is still working and you are covered under their plan. Medicare only steps in after the employer plan has paid its share.

The order in which plans pay is called coordination of benefits. Understanding which plan is primary matters because it changes what you owe out of pocket and which claims get processed first. If the wrong plan is listed as primary, you may face delays, denials, or unexpected bills.

Key Takeaways

  • Group health insurance from an employer with 20 or more employees is primary over Medicare, regardless of your age.
  • If you are covered under a spouse's employer plan while also on Medicare, that employer plan pays first.
  • Workers' compensation and liability insurance (from accidents or lawsuits) are always primary over Medicare.
  • You must tell both your employer plan and Medicare about each other so they can coordinate correctly and avoid overpayment disputes.
  • Medicaid is primary over Medicare in most situations, meaning Medicaid pays first and Medicare pays second.

When employer coverage is primary over Medicare

If you are enrolled in Medicare and also covered by a group health plan through your job or your spouse's job, the employer plan is primary if the employer has 20 or more employees. This applies even if you are over 65 and have been on Medicare for years. The employer plan processes your claim first, pays according to its rules, and then Medicare receives the claim and pays what remains.

The 20-employee threshold is strict. If your employer has exactly 19 employees, Medicare becomes primary. If the company grows to 20, the rule flips. You do not have to do anything when the threshold changes — the plans are supposed to track this — but it is worth confirming with your employer's benefits office if you work for a small company near that number.

This rule also applies if you are retired but your spouse is still working and you are covered under their employer plan. As long as the spouse's employer has 20 or more employees, that plan is primary for you, even though you are on Medicare.

Workers' compensation and liability claims always come first

Workers' compensation insurance is always primary over Medicare, no matter the circumstances. If you are injured on the job and file a workers' comp claim, that insurance pays first. Medicare will not pay for any treatment related to that injury until workers' comp has paid or denied its portion.

The same rule applies to liability insurance — coverage that pays when someone else is found responsible for your injury. If you are hit by a car and the other driver's liability insurance covers your medical bills, that insurance is primary. If you win a lawsuit or settle a claim, that settlement is primary. Medicare will not pay for treatment covered by a liability settlement, and in some cases Medicare can recover money from your settlement if it paid bills that the liability claim should have covered.

Medicaid is primary over Medicare in most cases

If you are enrolled in both Medicare and Medicaid — a situation called "dual may be able to access" — Medicaid is usually the primary payer. Medicaid pays first, and Medicare pays second. This applies to most services covered by both programs.

The exception is certain services that only Medicare covers, such as some mental health treatment or hospice care. In those cases, Medicare is the only payer because Medicaid does not cover the service at all.

If you are dual may be able to access, you do not need to do anything to set up coordination — your state Medicaid program and Medicare communicate automatically. However, you should confirm with your state Medicaid office that both programs have your correct information, especially if you move or change addresses.

How to tell Medicare and your other insurance about each other

When you have Medicare and another insurance plan, you must report this to both. Start by telling your employer's benefits office or your spouse's benefits office that you are on Medicare. They need this information to coordinate correctly. Then contact Medicare to report your employer coverage.

You can report employer coverage to Medicare by calling 1-800-MEDICARE (1-800-633-4227), mailing a form to your local Social Security office, or updating your information online at Medicare.gov. Have your employer plan's name, policy number, and the date coverage began ready when you call.

If you have workers' compensation or liability coverage, report that to Medicare as well. Provide the claim number, the date of injury or incident, and the insurance company's contact information. Medicare uses this information to avoid paying claims it should not pay and to prevent overpayment disputes later.

What happens if the wrong plan is listed as primary

If Medicare is listed as primary when your employer plan should be, your employer plan may deny the claim, saying Medicare should have paid it. Medicare may then deny the claim, saying the employer plan should have paid it. You end up caught between two plans, each saying the other should pay, and your bill goes unpaid.

If this happens, contact both plans and provide proof of which one should be primary. For employer coverage, your employer's benefits office can send a letter stating the plan is primary. For workers' comp or liability claims, provide the claim number and insurance company contact information. The plans can then reprocess the claim in the correct order.

Disputes over primary payer can take weeks or months to resolve. In the meantime, the provider may send you a bill. You do not have to pay it while the plans are sorting out who owes what — tell the provider the claim is under dispute and ask them to wait for the plans to coordinate.

Special rules for people still working past 65

If you are working past age 65 and your employer has 20 or more employees, you do not have to enroll in Medicare Part B (medical insurance) right away. You can delay enrollment without penalty as long as you are covered by the employer plan. However, you must still enroll in Part A (hospital insurance) at 65, even if you do not use it.

When you do enroll in Part B — either while still working or after you retire — tell Medicare about your employer coverage. This ensures the plans coordinate from the start. If you enroll in Part B after leaving your job, you may have a window to enroll without a late penalty, but only if you report the employer coverage to Medicare within a certain timeframe. Your employer's benefits office can provide a letter stating you had creditable coverage, which you will need for this process.

Frequently Asked Questions

Does Medicare pay anything if my employer plan is primary?

Yes. Your employer plan pays first according to its rules. Medicare then receives the claim and pays what the employer plan did not cover, up to what Medicare would normally pay. You are responsible for any remaining balance, such as copays or coinsurance.

What if I do not tell Medicare about my employer coverage?

Medicare may pay claims it should not have paid, and it can ask you or the provider to repay that money later. You may also face delays when claims are denied and have to be reprocessed in the correct order. It is worth the phone call to report it upfront.

If I am on Medicare and Medicaid, do I need to choose one?

No. You keep both. Medicaid pays first for most services, and Medicare pays second. Both programs work together automatically, though you should confirm your information is current with your state Medicaid office.

Can I use my employer plan instead of Medicare?

No. Once you are enrolled in Medicare, you cannot drop it in favor of an employer plan. However, if you are still working and your employer has 20 or more employees, you can delay enrolling in Part B without penalty. Your employer plan will be primary until you enroll in Part B.

Who decides which plan is primary?

Federal law sets the rules — employer plans with 20 or more employees are primary over Medicare, workers' comp and liability are always primary, and Medicaid is primary over Medicare in most cases. The plans themselves do not decide; they follow these rules when processing claims.