Deductible vs Copay vs Coinsurance vs Out-of-Pocket Max
A plain-English guide to the four cost-sharing terms that determine every medical bill you receive — and how to use them to verify you are being charged correctly.
Why these four terms determine almost every bill you receive
When your insurance pays a claim, the remaining patient responsibility is calculated using four cost-sharing mechanisms: your deductible, your copay, your coinsurance, and your out-of-pocket maximum. Each one applies differently depending on the type of service, where in your plan year you are, and whether your provider is in-network. Understanding how they interact is not just useful trivia — it is the foundation of every billing dispute, because most errors occur when one of these components is applied incorrectly or out of sequence.
The deductible: what you pay before insurance shares costs
Your deductible is the amount you pay out of pocket each plan year before your insurance starts contributing to covered services. If your deductible is $1,500, the first $1,500 of covered medical expenses each year is entirely your responsibility. Once you meet it, cost-sharing kicks in. Important exceptions: most plans cover preventive services — annual checkups, vaccinations, certain screenings — at 100% before the deductible is met. Prescription copays may also apply before the deductible depending on your plan design. On your EOB, look for a column labeled "applied to deductible" to see how each claim was credited.
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Check My EOB NowCopays: fixed amounts for specific service types
A copay is a flat dollar amount you pay for a specific type of service, regardless of the total cost. Common examples: $25 for a primary care visit, $50 for a specialist, $15 for a generic prescription. Copays are typically due at the time of service and may apply either before or after your deductible depending on your plan. Some plans have copays for office visits that apply even before the deductible is met. Check your Summary of Benefits and Coverage to see which services trigger a copay and whether the deductible must be met first.
Coinsurance: your percentage share after the deductible
Coinsurance is the percentage of covered costs you pay after your deductible is satisfied. If your coinsurance is 20%, your plan pays 80% of the allowed amount for covered services and you pay 20%. Coinsurance is the most common source of bill surprises because patients often assume that meeting their deductible means the plan pays everything from that point forward. It does not — coinsurance continues until you reach your out-of-pocket maximum. On your EOB, look for a column labeled "coinsurance" or "your responsibility" to see how it was applied.
Out-of-pocket maximum: the ceiling on your annual exposure
Your out-of-pocket maximum (OOPM) is the most you will pay for covered in-network services in a plan year. Once you reach this threshold — which includes deductible, copays, and coinsurance combined — your plan pays 100% for the remainder of the year. Under the ACA, marketplace plans must cap in-network OOPM at a federally set limit (adjusted annually). Premiums do not count toward the OOPM. Neither do out-of-network costs in most plans, which have separate out-of-network accumulators. Log into your member portal to see your current year-to-date accumulator totals.
How these interact: a worked example
Suppose your plan has a $1,000 deductible, 20% coinsurance, and a $4,000 out-of-pocket maximum. You have a hospital procedure with an allowed amount of $5,000. You pay the first $1,000 (deductible). After that, you owe 20% of the remaining $4,000 allowed amount, which is $800. Your total responsibility for this claim is $1,800. Future claims this year will only trigger coinsurance — no more deductible — until your cumulative payments reach $4,000, at which point the plan pays 100%. If your EOB shows a different patient responsibility than this math produces, that discrepancy is a dispute trigger.
How errors in these fields appear on your EOB
The most common errors are: deductible applied when it should already be satisfied based on prior claims; coinsurance calculated on the billed amount rather than the allowed amount; copay applied twice for the same visit; and out-of-network cost-sharing applied to a service from an in-network provider. Each of these appears as a specific line on your EOB. Compare the patient-responsibility breakdown on your EOB to your plan document and to your current accumulator values in the member portal. Any discrepancy between what the EOB shows and what your plan terms say should be reported to member services with the claim ID and the specific field in question.
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FAQ
Does my deductible reset every January 1?
Most plans reset on the plan anniversary date, which is commonly January 1 but not always. Check your plan documents for your specific reset date, especially if you have an employer plan with a non-calendar plan year.
Which cost category causes the most billing surprises?
Coinsurance after deductible is the most common surprise because people expect zero cost immediately after the deductible is met. Coinsurance continues until the out-of-pocket maximum is reached.
Do these rules apply the same way out-of-network?
No. Out-of-network benefits usually use separate accumulators — a separate deductible and a separate out-of-pocket maximum. Costs paid toward your in-network deductible typically do not count toward the out-of-network deductible and vice versa.
Where do I check my current deductible and OOPM progress?
Log into your insurer's member portal and look for a cost summary, benefits accumulator, or spending overview. This shows year-to-date totals for deductible applied, out-of-pocket paid, and remaining balance for each accumulator. Reconcile these against your EOBs if the totals look wrong.
Sources & references
This guide is grounded in primary government sources. Verify the details that apply to your specific plan and claim.
- Your rights and protections against surprise medical billsCenters for Medicare & Medicaid Services
- How to appeal an insurance company decisionHealthCare.gov (CMS)
See our sources and methodology and editorial policy for how this guidance is built and reviewed.