Glossary
Coordination of Benefits (COB)
The federal and contractual rules that determine which insurer pays first when you have more than one health plan.
Also known as: COB, payer order
Quick answer
Coordination of Benefits (COB) is the formal process — rooted in federal law and the TRICARE For Life statute — that decides the order in which two or more health plans pay a single claim. For TFL beneficiaries, COB is the machinery that turns 'Medicare + TFL' into near-$0 medical bills.
Why it matters
COB is the single most important concept for anyone with both Medicare and TFL. It is the difference between a $0 hospital bill and a $20,000 hospital bill on the exact same surgery.
Why this matters at age 65
At age 65, the payer order legally flips: TRICARE stops being primary, Medicare becomes primary, and TFL slides into the secondary slot as a wraparound. Misunderstanding this flip is the #1 reason new TFL beneficiaries get surprise bills.
When you'll encounter it
Every single claim. COB is invisible most of the time because Medicare automatically crosses over claims to WPS (TFL).
Impact on Medicare
Medicare is the primary payer in the U.S. for TFL beneficiaries on Original Medicare. It applies its own approved amount, deductible, and 20% coinsurance.
Impact on TRICARE For Life
TFL is the secondary payer in the U.S. — it pays the Medicare-approved cost share (Part A and Part B deductibles, coinsurance, copays) for services covered by both programs, typically zeroing out your bill.
Impact on Medicare Advantage
If you enroll in a Medicare Advantage plan, the MA plan becomes primary and TFL becomes secondary behind the plan, paying plan-level copays and coinsurance for TRICARE-covered services.
VA Healthcare considerations
VA care is separate — VA does not coordinate with Medicare or TFL. Care received inside the VA is VA-paid; care outside the VA uses your Medicare/TFL chain.
Military-specific context
Other Health Insurance (OHI) — like a working spouse's employer plan or FEHB — can sit between Medicare and TFL and change the payment order. Always update OHI status with WPS.
Common misconceptions
- "I can pick which insurance pays first." — No. Federal COB rules and the TFL statute determine the order automatically.
- "If I have OHI, TFL pays second." — With OHI, TFL is almost always LAST in line — OHI, then Medicare, then TFL.
Common mistakes to avoid
- Failing to report OHI (like FEHB or an employer plan) to WPS — claims will deny.
- Giving providers only the TFL card and not the Medicare card.
- Paying provider bills before both the Medicare MSN and the TFL EOB have arrived.
Real-world scenario: A 70-year-old retiree has knee surgery. Total billed: $24,000.
Medicare approves $9,800 and pays 80% of $9,800 after deductible. TFL pays the Part B deductible plus the 20% coinsurance. Patient owes $0 — but only because the COB chain ran cleanly and the provider accepted assignment.
What should I do?
- 1Hand providers BOTH cards — Medicare first, TFL second.
- 2Report any Other Health Insurance to WPS at 1-866-773-0404.
- 3Always wait for the Medicare MSN AND TFL EOB before paying any provider bill.
- 4If a claim was denied because COB ran out of order, ask the provider to refile with the correct primary payer.
Questions people commonly ask
Continue learning
— suggested by the knowledge graph- How Medicare and TRICARE For Life claims are paidThe mechanics of the Medicare-to-TFL crossover system — what providers do, what WPS does, and what to do if a claim gets stuck.
- Understanding Original Medicare (Parts A & B) for veteransExactly what Part A and Part B cover, what they cost in 2026, and why both are required to keep TRICARE For Life.
- Enrolling in Medicare: timing, methods, and the military-specific rulesWhen and how to sign up for Medicare Parts A and B — and the timing that protects your TRICARE For Life activation.
- Balance BillingThe practice of a provider billing you for the difference between their charge and what insurance approved.
- Billing ErrorsMistakes — accidental or intentional — on Medicare or TFL claims, ranging from duplicate charges to outright fraud.
- ClaimA formal request to an insurer for payment of a covered service.
- Medicare AssignmentA provider's agreement to accept Medicare's approved amount as full payment for a covered service.
- Medicare Summary Notice (MSN)Medicare's quarterly statement listing every Part A and Part B claim processed for you — Medicare's version of an EOB.
- How does the Medicare-to-TFL claim crossover work?Medicare processes the claim, pays its share, and electronically forwards it to WPS using your sponsor SSN. WPS pays TFL's share directly to the provider — usually within 2–3 weeks.
- Who pays first, Medicare or TRICARE For Life?Medicare pays first for any service it covers. TFL pays second. The claim usually crosses over automatically — you should never pay out of pocket up front.
- How much does Medicare Part B cost?Most people pay the standard Part B premium (roughly $185/month in 2026). Higher-income retirees pay IRMAA on top. Lower-income retirees may qualify for help paying it.
- I have other insurance besides Medicare and TFL. Who pays first?Order varies. Active-employment group insurance pays before Medicare; retiree coverage like FEHB pays after Medicare and usually before TFL. TFL is almost always last.
- Medicare denied a service. Can I appeal?Yes. The first level for Original Medicare is a Redetermination filed with the Medicare Administrative Contractor (MAC) within 120 days of the denial notice (MSN).
Related lessons
Related glossary terms
Related Official Resources
Continue learning straight from the source. Every link below goes to an official government or DoD resource.
Last reviewed January 2026 against the 2026 Medicare & You and TRICARE For Life handbooks.