Glossary
Coinsurance
Your percentage share of a covered service — typically 20% under Medicare Part B.
Quick answer
Coinsurance is the portion of a covered service's cost you pay after meeting your deductible, expressed as a percentage (e.g., 20%). The insurer pays the remainder.
Why it matters
Original Medicare's 20% Part B coinsurance is UNLIMITED — without a secondary payer, a serious illness could mean tens of thousands in coinsurance. TFL eliminates this exposure entirely.
Why this matters at age 65
Civilian retirees often buy Medigap to cover the 20%. TFL gives you that exact protection for free — but only if Medicare paid first.
When you'll encounter it
Every Part B claim. Part A also uses per-day coinsurance after day 60 of a hospital stay.
Impact on Medicare
You owe 20% of the Medicare-approved amount for most Part B services after meeting the deductible.
Impact on TRICARE For Life
TFL typically pays the 20% Part B coinsurance and Part A daily coinsurance for services covered by both programs — bringing your share to $0.
Impact on Medicare Advantage
MA plans usually replace coinsurance with flat copays. TFL helps cover those plan copays as secondary.
Common misconceptions
- "Medicare caps my coinsurance." — Original Medicare has no out-of-pocket cap. Only MA plans (or wraparound coverage like TFL) limit your exposure.
- "Coinsurance and copays are the same." — Coinsurance is a percentage; copay is a flat dollar amount.
Common mistakes to avoid
- Buying Medigap on top of TFL — it's redundant and a waste of premium dollars.
- Paying the 20% at check-out instead of waiting for the TFL EOB.
Real-world scenario: Outpatient surgery. Medicare-approved amount $6,200. Deductible already met.
Medicare pays $4,960 (80%). TFL pays the $1,240 coinsurance. Patient owes $0.
What should I do?
- 1Never buy Medigap on top of TFL — TFL fills the same gap.
- 2Wait for the TFL EOB before paying any coinsurance balance billed by the provider.
- 3If you're considering MA, compare plan copays against the $0 coinsurance you already have on Original Medicare + TFL.
Questions people commonly ask
Continue learning
— suggested by the knowledge graph- 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.
- What is Medicare? A complete overview for retired militaryA plain-English, handbook-grounded overview of the federal health insurance program for people 65 and older, written specifically for retired service members and their families.
- Balance BillingThe practice of a provider billing you for the difference between their charge and what insurance approved.
- Benefit Period (Part A)The Part A timeframe used to measure hospital deductibles and coinsurance — it resets after 60 days out of the hospital.
- Billing ErrorsMistakes — accidental or intentional — on Medicare or TFL claims, ranging from duplicate charges to outright fraud.
- Brand-Name DrugsFDA-approved drugs sold under a manufacturer's proprietary name — middle copay tier on the TRICARE formulary.
- ClaimA formal request to an insurer for payment of a covered service.
- Coordination of Benefits (COB)The federal and contractual rules that determine which insurer pays first when you have more than one health plan.
- Can my state help pay my Part B premium?If your income is low enough, yes. Medicare Savings Programs (QMB, SLMB, QI) pay the Part B premium for qualifying beneficiaries. Apply through your state Medicaid office.
- Does TFL cover mental health and substance use treatment?Yes. Medicare covers outpatient and inpatient mental health; TFL pays the coinsurance. VA may also provide mental health care for eligible veterans at no cost.
- Does TFL cover a skilled nursing facility stay?Yes. After a qualifying 3-day inpatient hospital stay, Medicare covers up to 100 days of SNF care and TFL pays the days-21–100 coinsurance.
- 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.
- Is there an enrollment fee for TRICARE For Life?No. TFL has no enrollment fee and no monthly premium. The only premium you pay is for Medicare Part B.
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.