When does Medicare pay second?
If you have Medicare and another insurance — an employer group plan, workers' comp, no-fault auto, liability, VA, or TRICARE — there are specific rules about which one pays first. Get this wrong and your claims get denied, your provider sends you the bill, or Medicare comes after you for repayment from a settlement. Twenty years inside taught me — the Medicare Secondary Payer rules are one of the most-ignored corners of the program, and the mistakes are expensive.
Dr. Ed Weir, PhD · 20 years inside Social Security · "Former" Sergeant, USMC
Updated April 2026
When does Medicare pay second?
Medicare pays second when another payer is responsible first. The most common triggers: working at age sixty-five-plus for an employer with twenty or more employees (employer plan primary), Medicare under sixty-five by disability with an employer of one hundred or more (employer plan primary), workers' compensation for a work-related injury, auto/no-fault/liability for an accident, or the first thirty months after Medicare eligibility based on End-Stage Renal Disease.
Coordinating Medicare with other coverage gets technical fast. The Medicare Coordination of Benefits and Recovery Center handles MSP situations directly, and Chapter's licensed advisors can sit with you and translate.
Free help from licensed Medicare advisors
Chapter's licensed advisors don't sell you a plan you don't need — they help you read your existing coverage, decode the MSP rules, and figure out who should be paying first. The conversation is free, the advisors are licensed, and they have no incentive to push a product on you.
Here's what to do, in 4 steps.
Here's the order I'd work through if I had Medicare plus another insurance and didn't know which was paying first.
1. Identify every coverage you have
Make a one-page list: Medicare Part A/B effective dates, any employer or retiree plan (and the employer's size), workers' comp claims still open, auto/no-fault policies, VA enrollment, TRICARE status, and any pending liability case. This list is the input to every MSP decision — you cannot get the order right without it.
42 CFR § 411.20 (MSP scope) ›2. Return your MSP questionnaire
If CMS or your Medicare Administrative Contractor sends you a Medicare Secondary Payer questionnaire (also called the Initial Enrollment Questionnaire or COB Initial Enrollment Form), fill it out and send it back. Failing to respond is a top-tier reason claims get denied or delayed — the system literally cannot tell who pays first without it.
CMS COB&R Center: 1-855-798-2627 ›3. Tell Medicare when coverage changes
When you start or stop a job with employer coverage, get into a car accident, file a workers' comp claim, or settle a liability case — call the Medicare Coordination of Benefits and Recovery Center at 1-855-798-2627. Reporting changes prevents Medicare from paying primary by mistake and then trying to recover from you later.
CMS COB&R Center ›4. Get help if a settlement is involved
If you have a workers' comp, no-fault, or liability settlement on the table — or you've been told you owe Medicare a conditional-payment refund — talk to a SHIP counselor at or call the COB&R Center. Workers' Comp Medicare Set-Asides have their own rules, and getting the allocation wrong can cost you Medicare coverage on related care for years.
SHIP National () ›The numbers that decide who pays first
Which of these sounds more like you?
MSP situations look different depending on what other coverage you have. Pick the one that sounds most like you.
I'm 65+, still working, employer has 20 or more employeesEmployer plan pays first; Medicare pays second
Under 42 CFR § 411.172, your employer's group health plan is primary and Medicare is secondary. The 20-employee threshold counts current and preceding-calendar-year employees on at least 20 calendar weeks (§ 411.170(a)(2)(i)).
File claims with the employer plan first. Medicare can pay the secondary share against deductibles and coinsurance up to the limits in 42 CFR § 411.33. You don't have to drop the employer plan — in most cases, you shouldn't.
I've seen people drop perfectly good employer coverage at 65 because they thought Medicare automatically takes over. If your employer has 20 or more employees, the law requires the plan to keep treating you the same as a worker under 65 — and Medicare is secondary. Don't drop coverage you've already paid for.
I'm 65+, working, employer has fewer than 20 employeesMedicare is primary; employer plan pays second
Small employers (under 20 employees) are not subject to the working-aged MSP rule. Medicare pays first; the employer plan is secondary or wraparound. This is a meaningful enrollment trap — if you delayed Part B because you assumed your employer plan was primary, you may owe a Part B late enrollment penalty.
If your employer is part of a multi-employer plan that includes at least one large employer, the large-employer rule may still apply; check with the plan administrator and CMS COB&R.
Don't get caught by this — if your employer has fewer than 20 employees, Medicare is primary and you generally need Part B starting the month you turn 65. Skipping Part B because you have small-employer coverage usually means a permanent late-enrollment penalty plus gaps in primary coverage.
I'm under 65 on Medicare via disability, employer has 100+ employeesLarge group health plan pays first; Medicare second
Under 42 CFR § 411.204 and § 411.102(c), a Large Group Health Plan (100 or more employees) of an employer covering you or a family member with current employment status pays primary; Medicare pays secondary.
The LGHP is forbidden by § 411.108 from "taking into account" your Medicare entitlement — they cannot drop you, raise your premiums, cut benefits, or steer you onto Medicare-first.
I've seen LGHPs quietly cut benefits the month a disability beneficiary's Medicare kicks in. That's illegal — § 411.108 lists eleven examples of forbidden actions, and I've seen CMS reverse plan decisions when beneficiaries pushed back with the regulation.
I'm on Medicare for End-Stage Renal Disease and have an employer planGroup plan primary for the first 30 months; Medicare second
ESRD has its own MSP timeline. The group health plan (any size) pays primary during a coordination period of 30 months that starts when you become Medicare-eligible based on ESRD. After 30 months, Medicare flips to primary.
The group plan cannot "take into account" ESRD-based Medicare eligibility, and cannot differentiate against ESRD enrollees (§ 411.102(a)). Your kidney pages and the dialysis-or-transplant page on this site cover the rest of the timeline.
I'm a flashlight, not a courtroom — the 30-month ESRD coordination period has fine print on COBRA, on transplants, and on retroactive Medicare eligibility. If your dialysis center or transplant team gives you a different month-count than this, get the specific facts of your case in front of CMS COB&R or a SHIP counselor.
I had a workers' compensation injuryWorkers' Comp pays first for related care
Under 42 CFR § 411.40, Medicare does not pay for services that workers' compensation has paid for, can reasonably be expected to pay for, or would have paid for if you had filed a proper claim. WC is primary for the work-related injury; Medicare is primary only for unrelated care.
If your WC settlement includes future medical care, a Workers' Comp Medicare Set-Aside (WCMSA) may need to be funded — that money has to be exhausted on related care before Medicare pays for the related condition (42 CFR § 411.46).
Don't get caught by this — if you settle a WC claim without addressing Medicare's interest in future medical care, CMS can refuse to pay for related treatment for years. The settlement document should explicitly account for Medicare — talk to a workers' comp attorney before you sign.
I had a car accident or filed a liability claimAuto/no-fault/liability primary for accident-related care
Under 42 CFR § 411.50, no-fault auto and liability insurance are primary for care related to the accident. Medicare may make a conditional payment if the liability insurer won't pay promptly (within 120 days), but Medicare must be reimbursed from any settlement or judgment (§ 411.24(h) — within 60 days of receipt).
Report pending liability and no-fault cases to the CMS Coordination of Benefits and Recovery Center early. CMS will issue a conditional-payment summary statement and, after settlement, a recovery demand letter.
I'm a flashlight, not a courtroom — conditional payments, procurement-cost reductions under § 411.37, and the MSP Recovery Portal are how Medicare gets repaid from settlements. The numbers can move into five and six figures. Talk to a personal-injury attorney who knows MSP, not just one who knows car accidents.
I'm helping a parent or spouse sort out who pays firstWhat you'll need before you call CMS or SHIP
Before you pick up the phone, gather: their Medicare card (HICN/MBI), employer plan card, employer name and approximate size, dates of any recent accidents, any open WC claim numbers, VA enrollment status if a veteran, TRICARE status if active-duty connected, and any pending liability case attorney name.
The Medicare Coordination of Benefits & Recovery Center at 1-855-798-2627 will speak to a representative if there's an authorization on file. A SHIP counselor can sit on a call with you and the family member — free, confidential, and trained on MSP. Find local SHIP at .
I'm a flashlight, not a courtroom — if your family member has dementia, recent surgery, or any cognitive change, set up authorization to speak with CMS on their behalf before you call. Otherwise the COB&R Center can't legally tell you anything.
My situation is something elseVA, TRICARE, Federal Black Lung, or a multi-coverage stack
MSP gets technical when more than two payers are involved or when federal programs (VA, TRICARE, Federal Black Lung) are in the mix. General rules: VA pays for service-connected care directly; TRICARE coordinates with Medicare under separate DoD/CMS rules; Federal Black Lung pays primary for related conditions (42 CFR § 411.40(b)(1)(ii)).
For anything outside the standard working-aged / disability / ESRD / WC / auto-liability fact patterns, call the CMS Coordination of Benefits & Recovery Center at 1-855-798-2627 or a SHIP counselor at . They handle the unusual stacks every day.
Still not sure? The Medicare Coordination of Benefits & Recovery Center at 1-855-798-2627 is the official CMS hotline for MSP questions. SHIP at gives free, unbiased help. Use either — don't guess.
Other programs that interact with Medicare
Medicare doesn't live alone. If you have other coverage now, or you're checking on benefits a parent or spouse may also qualify for, here are the programs that most often coordinate.
Working past 65 with employer coverage
If you're 65 or older, still working, and your employer has 20 or more employees, the employer plan pays first and Medicare pays second. The Working-Past-65 page walks through Part B enrollment timing and the Special Enrollment Period when your employer coverage ends.
COBRA and Medicare
COBRA continuation coverage is treated differently than active-employment coverage. When COBRA is the only other coverage, Medicare is generally primary. If you may qualify for COBRA after losing employer coverage, the COBRA-and-Medicare page explains how the order changes.
Medicare and ESRD (kidney failure)
If you may qualify for Medicare based on End-Stage Renal Disease, your group health plan is primary for the first 30 months and Medicare flips to primary after that. The ESRD page covers the eligibility timeline and how this coordination period interacts with COBRA.
Late Enrollment Penalty (LEP)
Skipping Part B because you assumed an employer plan was primary — when it wasn't — is a top reason people end up with a Part B late enrollment penalty. If you may have an LEP issue tied to a small-employer or COBRA situation, the LEP page covers appeals and recalculation.
Medicaid + Medicare (dual eligible)
Medicaid is generally the payer of last resort — it pays after Medicare, after employer coverage, and after WC/auto/liability. If you may qualify for both Medicare and Medicaid, the dual-eligible page explains how the two programs coordinate and what Medicare Savings Programs cover.
VA health care
VA and Medicare don't coordinate the way two civilian payers do. VA pays VA providers; Medicare pays civilian providers. If you may qualify for both, the VA-and-Medicare page covers when each one is the right card to hand the front desk.
Everything people ask me about MSP
When is Medicare the primary payer?
Medicare is primary when no other payer is responsible first. Common scenarios: you're retired and have only Medicare; your employer has fewer than 20 employees (working-aged rule); you're past the 30-month ESRD coordination period; or any care unrelated to a workers' comp injury, auto accident, or liability case. The reverse — Medicare as secondary — is the more complicated and more common-trip-up situation.
When does Medicare pay second?
Medicare is secondary when another payer is responsible first. The five most common triggers: (1) you're 65+ and your employer has 20 or more employees; (2) you're under 65 with disability-based Medicare and your employer has 100 or more employees; (3) the first 30 months of ESRD-based Medicare; (4) workers' compensation paying for a work-related injury; (5) auto/no-fault/liability paying for accident-related care.
How does the 20-employee rule actually count employees?
Under 42 CFR § 411.170(a)(2)(i), an employer is treated as having 20 or more employees if it had 20 or more employees on each working day in each of 20 or more calendar weeks in the current calendar year or the preceding calendar year. Affiliated companies are aggregated under the IRC section 52 and 414(m) rules in 42 CFR § 411.106. So a part-time-heavy small company can still cross the threshold, and a chain of related companies can be aggregated.
If I'm on disability Medicare and my spouse has employer coverage, who pays first?
If you're under 65 on Medicare based on disability and you're covered under your spouse's employer plan based on the spouse's current employment status, the LGHP rule applies if the spouse's employer has 100 or more employees. The plan pays first and Medicare pays second. If the employer is smaller, Medicare is primary.
What is a Workers' Comp Medicare Set-Aside (WCMSA) and do I need one?
A WCMSA is the portion of a workers' comp settlement designated to pay for future Medicare-covered medical care related to the injury. The WCMSA must be exhausted on related care before Medicare will pay for that condition (per 42 CFR § 411.46). CMS reviews WCMSA proposals over certain thresholds; the most current review thresholds and the WCMSA Reference Guide are published on cms.gov. If you're settling a WC claim, talk to a workers' comp attorney before signing.
I had a car accident. Will Medicare pay my medical bills?
Auto no-fault and liability insurance are primary for accident-related care under 42 CFR § 411.50. If the auto insurer won't pay promptly (within 120 days), Medicare may make a conditional payment — but Medicare must be repaid from any settlement or judgment within 60 days under § 411.24(h). Report the case to the CMS Coordination of Benefits & Recovery Center early so conditional-payment tracking starts on day one.
What is the MSP questionnaire and do I have to answer it?
The Medicare Secondary Payer questionnaire (sometimes called the Initial Enrollment Questionnaire) is a CMS form asking about all your other coverage. CMS uses it to figure out who pays first for your claims. Yes, you have to answer it. Failure to respond is a top reason claims get denied or delayed — the system literally cannot tell who pays first without your answers.
Will Medicare ever pay before VA?
VA and Medicare don't coordinate the way two civilian insurers do. The VA generally pays for care delivered at VA facilities or by VA-authorized providers; Medicare generally pays for care from civilian providers Medicare contracts with. For service-connected conditions, the VA is the primary payer. There's no traditional "primary/secondary" coordination on the same claim — you choose where to get care.
Does TRICARE coordinate with Medicare?
Yes. Once you become entitled to Medicare Part A, you generally need to enroll in Part B to keep TRICARE — the program then becomes TRICARE for Life, which acts as wraparound coverage with Medicare paying first for Medicare-covered services and TRICARE paying second. The exact rules vary by status (active duty, retiree, family member); confirm with your TRICARE Regional Contractor and the COB&R Center.
Where do I get help with a complicated MSP situation?
Two free resources. (1) CMS Coordination of Benefits & Recovery Center: 1-855-798-2627 — the official CMS hotline for MSP questions, conditional-payment information, and recovery cases. (2) SHIP (State Health Insurance Assistance Program) at — free, unbiased counseling on Medicare and MSP, with counselors trained on the working-aged, disability, ESRD, and WC/auto/liability fact patterns.
Sources
Every figure and rule on this page is verified against primary sources. Last verified 2026-04-28.
- For ESRD-based Medicare beneficiaries, the group health plan is primary during a coordination period (currently 30 months) that begins when the individual first becomes Medicare-eligible based on … —ssa.gov(verified 2026-04-28)
- An employer Group Health Plan is primary to Medicare, and Medicare is secondary, when the plan covers a Medicare beneficiary age 65 or older through the individual's or a spouse's current employment … —ecfr.gov(verified 2026-04-28)
- An employer is treated as having 20 or more employees if it had 20 or more employees on each working day in each of 20 or more calendar weeks in the current calendar year or the preceding calendar … —ecfr.gov(verified 2026-04-28)
- A Large Group Health Plan (an employer of 100 or more full-time or part-time employees) of an employer covering a disability-based Medicare beneficiary under 65 by virtue of the individual's or a … —ecfr.gov(verified 2026-04-28)
- Group Health Plans of any size cannot "take into account" Medicare eligibility based on End-Stage Renal Disease, and may not differentiate against ESRD enrollees. —ecfr.gov(verified 2026-04-28)
- Medicare does not pay for any services for which payment has been made or can reasonably be expected to be made under a workers' compensation law or plan of the United States or a state. —ecfr.gov(verified 2026-04-28)
- If a workers' compensation lump-sum settlement allocates amounts for specific future medical services, Medicare does not pay for those services until medical expenses related to the injury equal the … —ecfr.gov(verified 2026-04-28)
- Medicare does not pay for services for which payment has been made or can reasonably be expected to be made under automobile no-fault insurance, or under any non-automobile no-fault insurance for … —ecfr.gov(verified 2026-04-28)
- If Medicare makes a conditional payment because a primary payer hasn't paid promptly, the beneficiary or other party who receives a primary payment must reimburse Medicare within 60 days. —ecfr.gov(verified 2026-04-28)
- "Promptly," with respect to payment by a liability insurer, means payment within 120 days after the earlier of the date a claim is filed or the date the service was furnished (or the date of discharge … —ecfr.gov(verified 2026-04-28)
- GHPs and LGHPs are prohibited from "taking into account" Medicare entitlement; examples include failing to pay primary benefits, denying or terminating coverage based on Medicare entitlement, charging … —ecfr.gov(verified 2026-04-28)
- An employer or other entity is prohibited from offering Medicare beneficiaries financial or other benefits as incentives not to enroll in, or to terminate enrollment in, a GHP that is or would be … —ecfr.gov(verified 2026-04-28)
- When Medicare pays secondary, the secondary payment is the lowest of: (a) actual charges minus the primary payer payment, (b) what Medicare would pay if not covered by primary, or (c) the higher of … —ecfr.gov(verified 2026-04-28)
- CMS is subrogated to any individual, provider, supplier, physician, private insurer, State agency, attorney, or any other entity entitled to payment by a primary payer with respect to services for … —ecfr.gov(verified 2026-04-28)
- Beneficiaries, attorneys, representatives, and applicable plans can access conditional payment information and obtain final conditional payment amounts via the CMS Medicare Secondary Payer Recovery … —ecfr.gov(verified 2026-04-28)
Helping a parent or spouse?
If you're sorting out Medicare Secondary Payer rules for a parent who's still working past sixty-five, a spouse on disability with employer coverage, or a family member with a workers' comp settlement on the books — the moves are the same, but you'll need their MSP questionnaire, their other-insurance details, and (if there's a settlement) the original settlement documents. I'll walk you through what to ask.
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