You had a $2,500 deductible. You had surgery in March, paid the $2,500, and assumed the rest of the year was covered. In July the bills are still arriving and you are $6,500 deeper.
Nothing has gone wrong with your insurance. The deductible was never the cap. It was the entry fee.
Three numbers, not one
Almost every health plan has three cost-sharing numbers that do different jobs, and most people only remember the first one.
The deductible is what you pay for covered services before the plan starts paying at all. HealthCare.gov defines it as what you owe “before your plan starts to pay,” with the important exception that ACA-compliant plans cover certain preventive services in full even before you’ve met it.
Coinsurance is your share after the deductible. Typically 20% or 30% of the allowed amount for each covered service. This is the number people forget exists. Meeting the deductible does not move your share to zero; it moves it from 100% to 20%.
The out-of-pocket maximum is the real ceiling. Once your deductible, copays, and coinsurance add up to this number in a plan year, the plan pays 100% of covered in-network services for the rest of the year.
The deductible tells you when help starts. The out-of-pocket maximum tells you how bad the year can get.
The math on a $40,000 year
Assume a plan with a $2,500 deductible, 20% coinsurance, and a $9,000 out-of-pocket maximum. You have $40,000 in allowed costs — a surgery, follow-ups, imaging.
| Step | Your share |
|---|---|
| First $2,500 (deductible) | $2,500 |
| 20% of the remaining $37,500 | $7,500 |
| Subtotal before the cap | $10,000 |
| Capped at out-of-pocket maximum | $9,000 |
You paid $2,500 in March and $6,500 across the rest of the year. The deductible covered 28% of what you ended up owing.
Working the same numbers backward tells you something more useful: with a $2,500 deductible and 20% coinsurance, you hit the $9,000 ceiling at $35,000 in allowed costs. Below that, every additional dollar of care costs you twenty cents. Above it, care is free. The out-of-pocket maximum is the only number in the plan that ever makes your marginal cost of care zero.
The ceiling that actually exists
There is a legal limit on how high that ceiling can go. Section 2707(b) of the Public Health Service Act, added by the ACA, requires non-grandfathered group health plans — including self-insured and large-group employer plans — to hold annual cost sharing under a limit that HHS sets each year.
For the 2026 plan year, HealthCare.gov puts that limit at $10,600 for an individual and $21,200 for a family. For 2025 it was $9,200 and $18,400.
That is the worst legal case for in-network essential health benefits. It is also a number worth sitting with: a plan can be fully compliant, fully legitimate, and still leave a household on the hook for more than $21,000 in a bad year.
Plans that sit outside these rules — short-term limited-duration policies, health care sharing ministries, grandfathered plans — are not bound by that ceiling at all.
The four things that don’t count toward it
This is where people get hurt, because the out-of-pocket maximum feels like a promise and it has explicit exclusions. HealthCare.gov lists them:
- Your monthly premiums. You pay these whether you use care or not, and none of it counts.
- Anything your plan doesn’t cover. A service excluded from your benefits is 100% yours forever, no matter how much you’ve already spent this year.
- Out-of-network care. Plans are not required to count out-of-network cost sharing toward the limit, and many don’t. You can max out in-network and still face a separate, higher, sometimes uncapped out-of-network accumulator.
- Charges above the allowed amount. If an out-of-network provider bills more than what your plan considers the allowed amount for a service, that excess — balance billing — is outside the cap.
The No Surprises Act, enacted in December 2020 and in effect since January 2022, closed the worst version of the fourth one: for emergency care and for out-of-network providers working at in-network facilities, you generally can’t be balance billed beyond in-network cost sharing. Outside those situations, the exposure is real.
What to actually check
Three things, and they take about ten minutes with your Summary of Benefits and Coverage — the standardized document every plan has to give you.
- Find the out-of-pocket maximum, not just the deductible. If you are comparing plans, compare these first. A plan with a lower deductible and a higher ceiling can be the worse plan in exactly the year you need it to be good.
- Check whether the family out-of-pocket maximum is embedded or aggregate. Embedded means no single person can be charged more than the individual limit. Aggregate means the whole family amount has to be spent before the plan pays in full for anyone.
- Check whether out-of-network spending accumulates separately. It usually does. That determines whether “in-network only” is a preference or a requirement for you.
The deductible is the number on the front of the brochure because it is the number that sells the plan. The out-of-pocket maximum is the number that describes the risk you are actually holding.