Copay and coinsurance are the two ways a health plan makes you pay part of a bill after the deductible. They sound interchangeable in plan brochures. They are not. One is a flat fee you can look up before you walk in the door, and the other is a percentage of a number you will not see until the claim is processed.
Everything below is checked against the federal definitions and the KFF employer survey data current as of September 2026. If you are paying cash instead of using a plan, skip to the last section: the only question that matters there is whether a provider’s self-pay rate is lower than the share your plan would have charged you.
What Is a Copay?
HealthCare.gov defines a copayment as “a fixed amount ($20, for example) you pay for a covered health care service after you’ve paid your deductible.” The number is set by the plan, printed on your insurance card, and does not move when the underlying bill moves. A $30 office-visit copay is $30 whether the practice billed $140 or $400.
KFF’s 2025 Employer Health Benefits Survey, the most recent edition as of September 2026, puts the real-world averages at $27 for a primary care visit, $45 for a specialist visit, $313 for a hospital admission, and $186 for outpatient surgery.
There is one wrinkle that trips people up. HealthCare.gov’s own copayment page notes that if you have not met your deductible, you pay the entire allowed amount (the full $100 on a $100 visit) rather than the $20 copay. Whether your office-visit copay applies before or after the deductible is a plan-by-plan design choice, and it is the single most common source of surprise bills in the first quarter of a plan year. That question has its own page: does a copay count toward the deductible.
What Is Coinsurance?
HealthCare.gov defines coinsurance as “the percentage of costs of a covered health care service you pay (20%, for example) after you’ve paid your deductible.” KFF found the 2025 employer-plan average was 19% for both primary care and specialist visits, and 20% for a hospital admission.
The percentage is fixed. The base it is applied to is not. That is the entire risk profile of coinsurance in one sentence, and it is why a plan with “only 20% coinsurance” can still hand you a five-figure bill.
Copay vs Coinsurance at a Glance
| Copay | Coinsurance | |
|---|---|---|
| What you pay | Flat dollar amount | Percentage of the allowed amount |
| Known before the visit | Yes, it is on your card | No, not until the claim is priced |
| 2025 employer-plan average | $27 primary care, $45 specialist | 19% office visits, 20% hospital admission |
| Exposure on a large bill | Capped at the fee | Scales with the bill |
| Where it usually applies | Office visits, urgent care, ER, lower drug tiers | Hospital stays, surgery, imaging, specialty drugs |
| Applies before the deductible? | Often yes, by plan design | Almost never |
| Counts toward the out-of-pocket maximum? | Yes, for in-network covered care | Yes, for in-network covered care |
Averages come from the KFF 2025 Employer Health Benefits Survey. Definitions come from HealthCare.gov and the CMS uniform glossary.
Coinsurance Is Calculated on the Allowed Amount, Not the Bill
This is the part almost every explanation skips, and it is worth real money.
HealthCare.gov defines the allowed amount as “the maximum amount a plan will pay for a covered health care service,” also called the eligible expense, payment allowance, or negotiated rate. Your coinsurance percentage is applied to that number, not to the provider’s chargemaster price.
So if a hospital bills $3,000 for an outpatient procedure and your plan’s negotiated allowed amount is $1,200, your 20% coinsurance is $240, not $600. The remaining $1,800 of the billed charge is a contractual write-off that nobody pays.
The exception is out-of-network care. The CMS uniform glossary spells it out: “if the provider’s charge is $200 and the allowed amount is $110, the provider may bill you for the remaining $90.” That is balance billing, and it happens most often with non-contracted providers. In-network providers cannot balance bill you for covered services, and federal law now blocks most surprise out-of-network balance bills for emergency care and for out-of-network clinicians at in-network facilities. See the No Surprises Act for which bills are protected and which are not.
Practical consequence: you cannot calculate your coinsurance from a price quote. You need the allowed amount, which means calling the plan or pulling the payer-specific negotiated rate from the facility’s price transparency file.
A Worked Example With Real Dollars
HealthCare.gov’s coinsurance page runs this scenario. Say you rack up $12,000 in allowed costs during the plan year, your deductible is $3,000, and your coinsurance is 20%.
- You pay the first $3,000 yourself (the deductible).
- The remaining $9,000 is split: you pay 20%, which is $1,800, and the plan pays $7,200.
- Your total for the year is $4,800, assuming you have not hit the out-of-pocket maximum.
Now run the same year with copays instead. If those $12,000 in allowed costs were 20 specialist visits at the KFF average copay of $45, you would owe $900. Same care, wildly different exposure, because the copay ignores the price of what was delivered.
That structural difference shows up in national data. The Peterson-KFF Health System Tracker reports that people with employer coverage paid an average of $453 in deductibles, $193 in copayments, and $223 in coinsurance in 2023, for $869 total per enrollee. Deductibles accounted for 52% of cost sharing that year, up 12 percentage points from 2013, while copayments fell from 34% to 22%. Plans have been shifting away from the predictable form of cost sharing for a decade.
Prescription Drugs: Where the Two Collide
Drug benefits are where most people meet both mechanics in the same plan. KFF found that 92% of covered workers in 2025 were in a plan with tiered prescription cost sharing, and 84% were in a plan with three or more tiers.
| Drug tier | Average copay (2025) | Average coinsurance (2025) |
|---|---|---|
| First tier (usually generics) | $12 | 19% |
| Second tier (preferred brand) | $40 | 25% |
| Third tier (non-preferred brand) | $71 | 35% |
| Fourth tier | $123 | 31% |
| Separate specialty tier (large firms) | $111 | 27% |
Copays dominate the first three tiers. Coinsurance takes over as drugs get expensive, which is exactly backwards from a patient’s perspective. A 27% coinsurance on a specialty drug with a $6,000 monthly allowed amount is $1,620 a month. Among covered workers at firms with 200 or more employees who have specialty-tier coinsurance, KFF found that 62% have a maximum dollar limit on the amount of coinsurance they must pay, which means roughly a third do not.
For anything generic, the tier-1 copay is often higher than the cash price at a discount-card pharmacy. Comparing the two takes about ninety seconds: see GoodRx vs SingleCare.
How Both Fit With the Deductible and the Out-of-Pocket Maximum
Copays and coinsurance sit in the middle of a three-part structure. The deductible is what you pay before the plan starts sharing. Copays and coinsurance are what you pay while the plan is sharing. The out-of-pocket maximum is the ceiling where sharing stops and the plan pays 100% of covered in-network care. For 2026 the ACA caps that ceiling at $10,600 for self-only coverage and $21,200 for a family.
Two structural details are worth knowing. High-deductible plans push almost everything behind the deductible, so you see far fewer copays and far more full-price bills early in the year (HDHP vs PPO). And on family coverage, whether one person’s spending unlocks plan payment for everyone depends on embedded vs aggregate deductible design.
When the Cash Price Beats Your Copay or Coinsurance
For a self-pay reader the comparison is concrete. Ask the provider for the self-pay rate, then compare it to what your plan would charge you.
Coinsurance on imaging is the clearest win for cash. Radiology Assist lists self-pay MRIs starting at $250, with $265 for an MRI without contrast, and the flat rate includes the facility fee, the radiologist’s read, the images, and the written report. If your plan’s allowed amount for that same scan is $1,500 and your coinsurance is 20%, your share is $300. If you have not met the deductible, you owe the full $1,500. Cash wins in both cases. See MRI cost without insurance for the full spread.
Copays on routine visits usually beat cash. A $27 primary care copay is hard to undercut. Do not go looking for a cash discount on a $27 exposure.
Generics are a coin flip. A $12 tier-1 copay is real money on a drug that costs $4 with a discount card, and it is a bargain on one that does not.
The catch, and it is a real one. Money you pay at a cash price generally does not count toward your deductible or your out-of-pocket maximum, because no claim is filed. Saving $250 on an MRI in January is a clean win if you finish the year healthy. If you end up hospitalized in March, that $250 bought you nothing toward the ceiling. Weigh the cash discount against how likely you are to hit the maximum anyway, which is covered in detail on the out-of-pocket maximum page.
The Bottom Line
A copay is a price you can look up. Coinsurance is a percentage of a price you cannot look up, applied to the plan’s negotiated allowed amount rather than the billed charge. Copays dominate routine care and cheap drugs; coinsurance dominates hospitals, surgery, imaging, and specialty medications, which is to say it dominates everywhere the numbers get large. Before any expensive service, get the allowed amount from your plan and the self-pay rate from the provider, and pay whichever is lower after accounting for what you give up by not filing a claim.