Medicare · Cornerstone
Medicare secondary payer: who pays first and why it matters
Last reviewed July 30, 20267 min readBy the Goodsurance editorial team Reviewed by the Goodsurance editorial team
Medicare secondary payer (MSP) is the set of rules that decide whether Medicare pays first or second when you have more than one source of coverage. The payer that pays first is the primary payer; it processes the claim up to its coverage limits. The payer that pays second, the secondary payer, may cover some or all of the remaining cost. Medicare is not automatically the primary payer, and treating it as if it were is a common and expensive mistake.
1What "Medicare secondary payer" actually means
The short version
- Medicare pays second, not first, when another payer is legally responsible ahead of it.
- Employer size is the pivot: with 20 or more employees the group plan usually pays first; under 20, Medicare usually pays first.
- COBRA and retiree coverage never count as active employer coverage, which affects both payment order and late-enrollment penalties.
- Workers' compensation, no-fault, and liability claims almost always pay before Medicare.
When Medicare is secondary, the primary payer sends its payment and its explanation of benefits, and then Medicare considers the balance. Providers are supposed to bill in the correct order, but errors happen, so understanding your own situation helps you catch problems early.
In short: MSP rules set the payment order when you hold more than one type of coverage, and Medicare is frequently the second payer, not the first.
2Why the payment order exists
Congress built MSP rules to keep Medicare from paying for costs another party should cover. Before these rules, Medicare often paid first even when an employer plan or an accident settlement was on the hook, which shifted private costs onto the program. The Centers for Medicare & Medicaid Services (CMS) now runs a coordination of benefits process to identify other coverage and enforce the correct order.
For you, the practical effect is that Medicare will sometimes deny or delay a claim until the primary payer has acted. That is not a coverage gap; it is the order working as designed. The remedy is to make sure the primary payer processes the claim first, then let Medicare pick up its share.
In short: the payment order protects Medicare dollars, and denials tied to it usually mean a primary payer needs to act first.
3Employer coverage: the 20-employee rule
The single most important factor for working people and their spouses is employer size. With an employer that has 20 or more employees, the group health plan pays primary to Medicare, and Medicare pays second. With an employer that has fewer than 20 employees, Medicare pays primary and the group plan pays second.
This matters for two reasons. First, it determines whose card the provider bills first. Second, it shapes your enrollment strategy. If your active employer coverage is primary because the company has 20 or more employees, you generally have a Special Enrollment Period that lets you delay Part B without a penalty while you keep working.
That Part B Special Enrollment Period runs for 8 months, and it begins when your employment ends or your employer coverage ends, whichever comes first. Missing it can trigger the Part B late-enrollment penalty, which adds 10% for each full 12-month period you delayed Part B without qualifying coverage, and that penalty is permanent.
A frequent trap: COBRA and retiree coverage never count as active employer coverage for Special Enrollment Period or late-penalty purposes. If you leave a job and switch to COBRA, the clock on your 8-month window has already started, because it started when the active employment or active coverage ended. People who wait to enroll until COBRA runs out often discover they are already past the deadline.
In short: 20 or more employees means the group plan pays first and a Special Enrollment Period usually applies; under 20, Medicare pays first, and COBRA never counts as active coverage.
4Other situations where Medicare pays second
Employer coverage is the most common trigger, but several other arrangements put Medicare in the secondary position.
Workers' compensation
If your care relates to a work injury, workers' compensation is primary for the treatment tied to that injury. Medicare will not pay for services that workers' comp is responsible for. When a claim is contested and payment is delayed, Medicare may make a conditional payment and later recover it once the workers' comp case resolves.
No-fault and liability insurance
Car accident coverage, other no-fault insurance, and liability settlements generally pay before Medicare for care connected to the incident. As with workers' comp, Medicare may pay conditionally while a case is pending, then seek repayment from the settlement or judgment.
End-stage renal disease
People who qualify for Medicare because of end-stage renal disease (ESRD) have a coordination period during which an employer group plan pays primary, after which Medicare becomes primary. The timing rules here are specific, so this is a situation where it helps to confirm your own dates.
Disability and large employers
If you have Medicare because of a disability and are covered by a large group health plan (through your own or a family member's current employment), that plan can be primary. The size thresholds differ from the age-65 rules, so the details depend on the plan and employer.
In short: workers' comp, no-fault, liability, ESRD coordination periods, and certain disability-based large-plan situations can all place Medicare in the secondary role.
5Conditional payments and how recovery works
When another payer is responsible but has not paid, Medicare may issue a conditional payment so your care is not held up. "Conditional" means Medicare expects to be reimbursed once the responsible party pays. This is common in liability and workers' comp cases that take time to settle.
If you receive a settlement, judgment, or award, Medicare has the right to recover what it paid conditionally for the related care. The Benefits Coordination & Recovery Center handles this process. Practically, that means a portion of a settlement may need to reimburse Medicare, and ignoring a recovery notice can create larger problems later.
Keep records of any accident claim, work injury, or lawsuit connected to your medical care, and respond to Medicare's coordination notices promptly. The recovery process is more manageable when you engage with it early rather than after a case closes.
In short: Medicare can pay conditionally when another payer is slow, but it expects repayment once a settlement or responsible payer comes through.
6How to keep your claims paying correctly
Getting the payment order right is mostly about giving accurate information and keeping it current.
- Tell your providers about every source of coverage you hold, including employer plans, retiree plans, workers' comp, and any accident claim.
- Respond to the coordination of benefits questionnaires CMS or your plan sends; these keep Medicare's records accurate about who pays first.
- Track your enrollment windows. Your Initial Enrollment Period is 7 months: the three months before your birthday month, your birthday month, and the three months after.
- If you delayed Part B because of active employer coverage, act inside the 8-month Special Enrollment Period, and remember it starts when active coverage or employment ends, not when COBRA ends.
One more planning note that trips people up: any Medicare enrollment, including premium-free Part A, ends your eligibility to make new health savings account (HSA) contributions, and Part A can backdate up to 6 months. If you are still working, contributing to an HSA, and plan to delay Medicare, coordinate your enrollment timing carefully so a backdated Part A does not create excess HSA contributions.
If your situation involves multiple payers and you are unsure how they should coordinate, that is exactly the kind of question worth talking through. To find out more about coverage, please contact us to discuss plan options.
In short: accurate coverage information, timely responses to coordination notices, and attention to enrollment windows keep claims paying in the right order.
7Quick reference: common primary payer scenarios
| Your situation | Who usually pays first |
|---|---|
| Active employer coverage, 20+ employees | Group health plan |
| Active employer coverage, under 20 employees | Medicare |
| Retiree coverage | Medicare |
| COBRA | Medicare |
| Work injury under workers' comp | Workers' compensation |
| Car accident under no-fault | No-fault insurer |
| Liability settlement pending | Medicare may pay conditionally, then recover |
These are the general rules. Specific plans, union arrangements, and disability or ESRD timing can change the answer, so confirm your own case when the stakes are high.
In short: this table covers the usual order, but plan-specific and injury-related details can shift who pays first.
Common questions about Medicare
Quick answers to common questions
Tap any question to expand. Each question links to a fuller standalone answer.
Does Medicare cover durable medical equipment?
Yes.
Medicare Part B covers durable medical equipment (DME): reusable medical gear your doctor prescribes for use at home, such as wheelchairs, walkers, hospital beds, oxygen equipment, CPAP machines, and blood sugar monitors. You pay 20% of the Medicare-approved amount after the $283 Part B deductible in 2026, and Medicare pays the other 80%. To be covered, the item must be ordered by a Medicare-enrolled doctor and supplied by a Medicare-enrolled supplier, and some items are rented rather than bought. Equipment meant mainly for use outside the home, or only for comfort or convenience, is not covered.
Does Medicare cover mental health services?
Yes.
Medicare covers mental health care across its parts in 2026. Part B covers outpatient services like therapy, counseling, and visits with psychiatrists, psychologists, and clinical social workers, and since 2024 it also covers marriage and family therapists and mental health counselors. You pay 20% of the Medicare-approved amount after the $283 deductible, and one depression screening each year is free. Part A covers inpatient mental health care, with a lifetime limit of 190 days in a freestanding psychiatric hospital. Part D covers most mental health medications. Many of these services are also available by telehealth, and Medicare Advantage plans cover at least the same benefits.
Does Medicare cover vision care?
Mostly no for routine care.
In 2026, Original Medicare does not cover routine eye exams for glasses or contact lenses, and it does not pay for the glasses or contacts themselves. It does cover some medical eye care: yearly glaucoma screenings for people at high risk, diabetic retinopathy exams, treatment for eye diseases, and cataract surgery (including one pair of standard glasses or contacts afterward). For those covered services you pay 20% after the $283 Part B deductible. Many Medicare Advantage plans add a routine vision benefit covering eye exams and an allowance for glasses.
Does Medicare cover physical therapy?
Yes.
Medicare Part B covers outpatient physical therapy that is medically necessary to treat your condition. You pay 20% of the Medicare-approved amount after the yearly Part B deductible ($283 in 2026). There is no longer a hard dollar cap on therapy, but once your physical and speech therapy together pass $2,480 in 2026, your therapist must add a note (called a KX modifier) confirming you still need care. Claims above $3,000 may be reviewed for medical necessity. Part A covers physical therapy you receive as a hospital inpatient or in a skilled nursing facility. A doctor or therapist must set up and regularly review your plan of care.
Does Medicare cover chiropractic care?
Partly.
Medicare Part B covers one specific chiropractic service: manual manipulation of the spine to correct a subluxation (when one or more bones of the spine are out of position) that a doctor confirms is medically necessary. You pay 20% of the Medicare-approved amount after the $283 Part B deductible in 2026. Medicare does not cover other services a chiropractor might offer, such as X-rays, massage therapy, acupuncture, or routine wellness visits, so you would pay the full cost for those. Some Medicare Advantage plans include extra chiropractic or wellness benefits beyond this.
Does Medicare cover ambulance services?
Yes, in limited situations.
Medicare Part B covers emergency ambulance transportation when traveling any other way could endanger your health, taking you to the nearest appropriate hospital or facility. You pay 20% of the Medicare-approved amount after the $283 Part B deductible in 2026. Air ambulance is covered only when ground transport cannot reach you or would take too long. Non-emergency ambulance trips, for example to dialysis, are covered only when a doctor provides a written order stating they are medically necessary. Medicare does not cover ambulance rides taken purely for convenience.
Does Medicare cover skilled nursing facility care?
Yes, on a short-term basis.
Medicare Part A covers skilled nursing facility (SNF) care after a qualifying inpatient hospital stay of at least 3 days, when you need daily skilled care like nursing or therapy. In 2026 you pay $0 for days 1 through 20 of each benefit period, $217 per day for days 21 through 100, and all costs after day 100. Coverage is for skilled care while you recover, not for long-term or custodial care (help with daily activities like bathing or dressing), which Medicare does not cover. Long-term nursing home care is generally paid through Medicaid or private funds.
Does Medicare cover hearing aids?
No, not under Original Medicare.
In 2026, Original Medicare (Parts A and B) does not pay for hearing aids or the exams to fit them. Part B does cover diagnostic hearing and balance exams when your doctor orders them to help diagnose or treat a medical condition, and for those you pay 20% after the $283 deductible. Many Medicare Advantage plans, however, include a hearing benefit that helps pay for routine hearing exams and hearing aids, often through a specific network or allowance. If hearing coverage matters to you, it is worth comparing Advantage plans or a standalone hearing plan.
Does Medicare cover home health care?
Yes, when you qualify.
Medicare Parts A and B cover home health care if a doctor certifies that you are homebound (leaving home takes a major effort) and need part-time skilled care, such as skilled nursing, physical therapy, occupational therapy, or speech therapy. A Medicare-certified home health agency must provide the care under a plan your doctor reviews. You pay $0 for covered home health visits in 2026, and 20% for any durable medical equipment. Medicare does not cover 24-hour home care, meal delivery, or homemaker services like cleaning when that is the only care you need.
Does Medicare cover diabetes supplies and testing?
Yes.
In 2026 Medicare covers most diabetes care across two parts. Part B (outpatient care and equipment) covers blood sugar monitors, test strips, lancets, and continuous glucose monitors (CGMs) as durable medical equipment, plus diabetes screenings and a self-management training program. You pay 20% of the Medicare-approved amount after the $283 Part B deductible. Part D (drug coverage) covers insulin and related supplies like syringes, and in 2026 your insulin is capped at $35 for a month's supply. If you have a Medicare Advantage plan, it covers at least the same diabetes benefits, sometimes with added extras.
Which is better, Medigap or Medicare Advantage?
Neither is better for everyone; they suit different needs.
Medigap (also called Medicare Supplement, a private policy that pairs with Original Medicare) lets you see any doctor nationwide who accepts Medicare with no network and very predictable out-of-pocket costs, but you pay a monthly Medigap premium and add a separate Part D drug plan. Medicare Advantage (Part C, your Medicare benefits through a private plan) often has a lower or $0 plan premium, bundles drug coverage and extras like dental and vision, and caps your yearly out-of-pocket costs, but uses provider networks and may require prior approval. People who travel, want maximum doctor freedom, and prefer steady costs often lean Medigap; people who want low premiums, extras, and a network they are comfortable with often lean Medicare Advantage. With both, you still pay the Part B premium ($202.90 per month in 2026). To find out which fits your situation, reach out to a licensed Goodsurance advisor at 1-888-301-8091 (TTY 711), Mon to Fri 8 am to 5 pm PT.
Can I see out-of-network doctors on a Medicare Advantage PPO?
Yes.
A Medicare Advantage PPO (Preferred Provider Organization plan, where your Medicare benefits come through a private plan) lets you see doctors and hospitals outside the plan's network, but you usually pay more for out-of-network care than for in-network care. Staying in network keeps your costs lower, while going out of network is allowed and can be worth it if you want a specific provider. This flexibility is a key difference from a Medicare Advantage HMO (Health Maintenance Organization plan), which generally only covers in-network care except in emergencies. With a PPO, you also typically do not need a referral to see a specialist. Keep in mind the provider must accept the plan and Medicare. Emergency and urgent care are covered regardless of network on both plan types. The trade-off with a PPO is more freedom in exchange for generally higher costs than an HMO.
References
- Get started with MedicareCovers enrollment periods, the Part B Special Enrollment Period, employer-size payment rules, and HSA timing.
- Coordination of Benefits & Recovery overviewExplains how CMS determines payment order, conditional payments, and Medicare's recovery process.
- 2026 Medicare Parts A & B premiums and deductiblesSource for verified 2026 Part A and Part B cost figures referenced in Medicare cost planning.
- SSDI and Medicare eligibility timingDetails disability-based Medicare eligibility, which affects secondary payer rules for beneficiaries under 65.