What MSP Means in Medicare and How It Works

MSP stands for Medicare Secondary Payer, and it means Medicare is not your main insurance

Medicare Secondary Payer (MSP) is a rule that tells Medicare to pay second instead of first when you have other insurance coverage. If you have Medicare and also have coverage through an employer, a workers' compensation claim, an auto accident settlement, or another source, that other coverage is your primary payer. Medicare only pays what is left after your primary insurance has paid its share.

This rule exists because Medicare wants to avoid paying for care that another insurance should cover. If you do not tell Medicare about your other coverage, you may end up overpaying out of pocket, or Medicare may deny a claim it would have covered if it knew the real payment order.

MSP applies to specific situations. The most common are group health plans through current employment, workers' compensation, liability insurance (from car accidents or injury lawsuits), and no-fault auto insurance. It can also explore to Veterans benefits, Indian tribe plans, and TRICARE (military family coverage). The rules are different for each type of coverage.

Key Takeaways

MSP means Medicare pays second, not first, when you have other insurance that should cover the bill.
You must tell Medicare about any other coverage you have, or you may pay more out of pocket than you should.
Group health plans from your job, workers' compensation, and liability insurance are the most common reasons Medicare becomes secondary.
If you do not report MSP situations, Medicare may deny claims or you may owe money that your primary insurance should have paid.
The order of payment changes depending on your age, whether you are still working, and what type of coverage you have.

When Medicare becomes the secondary payer

If you are under 65 and covered by a group health plan through your own job or your spouse's job, that plan pays first. Medicare pays second. This is true even if you are on Medicare because of disability or end-stage renal disease. You must stay in the group plan as long as you are may be able to access, because dropping it to save money can create gaps in coverage that Medicare will not fill.

If you are 65 or older and still working, and your employer has 20 or more employees, your employer plan pays first and Medicare pays second. If your employer has fewer than 20 employees, Medicare pays first. This threshold matters because small employers are not required to offer health insurance, so Medicare becomes the main payer for those workers.

If you are retired but your spouse is still working and has a group health plan that covers you, that plan is primary and Medicare is secondary. The same rule applies if you are covered as a dependent on someone else's employer plan.

Workers' compensation always pays first for injuries or illnesses that arose from work. Medicare will not pay anything for that claim until workers' compensation has paid or denied it. If you receive a workers' compensation settlement, you may have to set aside money in a special account before Medicare will pay for related treatment.

How to report other coverage to Medicare

You report MSP situations by calling Medicare at 1-800-MEDICARE (1-800-633-4227) or by contacting your local Social Security office. Have your other insurance information ready: the name of the plan, the policy number, and the employer name if it is a group plan.

You can also report MSP when you enroll in Medicare Part B, or you can update your information anytime after enrollment. If your situation changes — for example, you retire and lose your employer coverage — call Medicare to let them know so they can update your records.

When you see a doctor or go to a hospital, bring your insurance card for both Medicare and your other coverage. Give both card numbers to the provider's billing office. The provider will then submit the claim to your primary insurance first, and if that insurance does not cover the full bill, they will submit the remainder to Medicare.

What happens if you do not report MSP

If Medicare does not know about your other coverage, it may pay claims that your primary insurance should have paid. When Medicare later discovers the MSP situation, it will ask for that money back. You could receive a bill for thousands of dollars, even though you thought the claims were covered.

Alternatively, Medicare may deny a claim because it thinks another insurance should cover it, but your primary insurance denies it because it thinks Medicare should pay. You end up caught between two insurers, both refusing to pay, and you are responsible for the bill.

If you receive a settlement from a liability case (such as a car accident lawsuit), Medicare has a right to recover money from that settlement for any medical care related to the injury. This is called Medicare's right of recovery. If you do not report the settlement, Medicare may place a lien on the money or pursue you for repayment.

MSP and coordination of benefits

When you have MSP, the two insurers coordinate their payments so that together they do not pay more than the actual bill. Your primary insurance pays up to what it normally covers. Medicare then pays its share of what remains, up to what Medicare would normally pay for that service.

You are responsible for any deductibles, copays, or coinsurance that your primary insurance requires. Medicare does not waive these costs just because it is secondary. After your primary insurance pays and you have paid your share, Medicare covers its portion of the remaining balance.

The exact payment order depends on the type of coverage. For example, if you have both a group health plan and workers' compensation, workers' compensation pays first, then the group plan, then Medicare. If you have both a group plan and liability insurance from a car accident, the liability insurance pays first, then the group plan, then Medicare.

MSP situations that require special handling

If you receive a workers' compensation settlement or a liability settlement (from a lawsuit or insurance claim), you may have to set aside money in a Medicare Set-Aside (MSA) account before Medicare will pay for future treatment related to that injury. The amount set aside depends on your age, the type of injury, and your expected medical costs. Medicare will not pay for related care until the MSA money is spent down.

If you are covered by TRICARE (military family insurance), TRICARE is primary and Medicare is secondary. You must keep your TRICARE coverage active to avoid losing it, because re-enrolling can be difficult. The same principle applies to Veterans benefits: VA coverage is primary for VA-covered services, and Medicare is secondary.

If you are on Medicare because of end-stage renal disease (ESRD) and you have a group health plan through your job or your spouse's job, that plan is primary for the first 30 months of your Medicare coverage. After 30 months, Medicare becomes primary. This 30-month window is important because it affects which insurance you should submit claims to first.

How to check your MSP status with Medicare

You can view your Medicare records online through your Medicare.gov account. Log in, go to your profile, and look for information about other insurance coverage. If the information is incorrect or missing, you can update it directly in your account or call Medicare to make changes.

If you are unsure whether your coverage qualifies as MSP, call Medicare at 1-800-MEDICARE. Have your insurance information ready, and ask specifically whether your other coverage makes Medicare secondary. Medicare staff can tell you the payment order and whether you need to report anything else.

Keep copies of all insurance cards, policy documents, and correspondence about your coverage. If a billing dispute arises, you will need proof of what coverage you had and when you reported it to Medicare.

Frequently Asked Questions

If I have a group health plan and Medicare, which one do I use first?

Your group health plan is primary. Submit claims to that plan first. If it does not cover the full bill, submit the remainder to Medicare. If you are under 65, your employer plan always pays first. If you are 65 or older and still working, your employer plan pays first only if the employer has 20 or more employees.

Do I have to stay in my employer health plan if I am on Medicare?

If you are under 65 and on Medicare, you should stay in your employer plan because it will be primary and Medicare will be secondary. Dropping it can leave gaps in coverage. If you are 65 or older, you can drop your employer plan and use Medicare alone, but check whether you will lose other benefits like dental or vision coverage.

What is a Medicare Set-Aside account?

A Medicare Set-Aside is money set aside from a workers' compensation or liability settlement that you must use for medical care related to the injury before Medicare will pay. The amount is calculated based on your age and expected medical costs. Once the MSA is spent down, Medicare becomes primary for that condition.

Can Medicare bill me back if I did not report other coverage?

Yes. If Medicare pays claims that your primary insurance should have covered, Medicare can ask you to repay that money. This can happen months or years after the claim was paid. Reporting all your coverage when you enroll in Medicare protects you from unexpected bills.

Does MSP explore if I have supplemental insurance (Medigap)?

No. Medigap is not primary insurance; it is supplemental. MSP applies only to coverage that is primary to Medicare, such as group health plans, workers' compensation, and liability insurance. Medigap works alongside Medicare, not instead of it.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.