Deductible, coinsurance, copay, and the 100/80/50 split are the four terms that decide what a patient actually pays, and they get muddled constantly. This guide separates them cleanly, shows how they stack up on a real bill, and explains how they interact with the annual maximum, so an estimate is accurate before the patient sits down, not a surprise after.
Last updated July 2026 · Reviewed by the PracticeAlpha billing team
The short answer. The deductible is what the patient pays before the plan pays anything, usually $50 to $100 a year. Coinsurance is how the cost is split after that, expressed as a percentage. The 100/80/50 model is the common structure: the plan pays 100 percent for preventive care, 80 percent for basic work, and 50 percent for major work, after the deductible. A copay is a flat dollar amount for a specific service instead of a percentage. Put those together and you can quote almost any patient accurately, which is the whole point.
The deductible is the amount the patient pays out of pocket before the plan starts contributing. It commonly runs between $50 and $100 per year, and once it is met, it does not apply again until the plan year resets. On a family plan there is often both an individual and a family deductible.
One detail matters for quoting: most plans waive the deductible for preventive care like cleanings and exams, so it usually only applies once the patient needs basic or major treatment. That is why a patient can go years only using preventive visits and never notice the deductible, then hit it the first time they need a filling.
Coinsurance is how the patient and the plan share the cost of a covered service after the deductible is met, and it is always a percentage. If a service is covered at 80 percent, the plan pays 80 percent of the allowed amount and the patient pays the other 20 percent. Because it is a percentage, the patient's share scales with the size of the bill.
Most plans organize coinsurance into three tiers, the 100/80/50 model:
The exact percentages vary by plan, and out-of-network care is usually paid at a lower share, calculated against the plan's allowed amount rather than the full fee, which is where fee schedules like UCR and MAC come in.
A copay is a set dollar amount for a specific service, and it is easy to confuse with coinsurance. The difference is that a copay does not change with the cost of the treatment, while coinsurance is always a percentage of it. A $25 copay for a visit is $25 whether the visit is simple or complex.
Two more distinctions matter for estimating. Coinsurance applies only after the deductible is met, while a copay can apply before or after. And copays typically do not count toward the deductible or the annual maximum. Most traditional dental plans lean on deductibles and coinsurance rather than copays, but plans structured more like an HMO may use copays instead, which is part of the difference explained in HMO vs PPO dental.
A wrong estimate is a collections problem waiting to happen. We verify deductible, coinsurance, and remaining maximum before treatment so the patient portion is right the first time.
See our verification serviceThe pieces only make sense when you stack them on a real bill. Take a $1,000 crown, a major service, on a plan with a $100 annual deductible the patient has not met yet and 50 percent coinsurance for major work:
Change any input, an already-met deductible, 80 percent coinsurance, an out-of-network allowed amount below the fee, and the number moves. That is exactly why an accurate estimate depends on verifying the specific plan's deductible, coinsurance, and remaining maximum before treatment, not assuming a standard split.
Think of a claim in layers. The deductible is the patient's upfront share. Coinsurance is the patient's percentage of what remains. The annual maximum caps what the plan pays across the whole year. They are separate mechanisms, and mixing them up is where estimates go wrong.
The key point patients miss: their own deductible and coinsurance payments do not count toward the annual maximum, because the maximum only measures what the plan spends, not what the patient does. So a patient can be paying plenty out of pocket and still not be drawing down the maximum. Getting all three right together, the deductible, the coinsurance split, and the remaining maximum, is what makes a treatment estimate trustworthy. If inaccurate estimates are turning into patient balances your office ends up writing off, a free AR analysis shows where it is leaking.
A deductible is the amount you pay out of pocket before the plan starts paying its share. It commonly runs between $50 and $100 per year, and once you have met it, you do not pay it again until the plan year resets. Many plans waive the deductible for preventive care such as cleanings and exams, so it usually applies to basic and major treatment.
Coinsurance is how you and the plan split the cost of a covered service after the deductible is met, expressed as a percentage. If a service is covered at 80 percent, the plan pays 80 percent of the allowed amount and you pay the remaining 20 percent. Because it is a percentage, your share rises and falls with the cost of the treatment.
It is the common structure for how much a plan pays by service category, after the deductible: often 100 percent for preventive care like cleanings and exams, 80 percent for basic procedures such as fillings, and 50 percent for major work like crowns. The exact percentages vary by plan, and out-of-network care is usually paid at a lower share.
Coinsurance is a percentage of the cost and changes with the size of the bill. A copay is a fixed dollar amount for a specific service that does not change with the cost. Coinsurance applies after the deductible is met, while a copay can apply before or after. Copays also typically do not count toward the deductible or maximum.
They are separate layers of the same bill. The deductible is your upfront share, coinsurance is your percentage of what remains, and the annual maximum caps what the plan pays across the year. Your deductible and coinsurance payments do not count toward the maximum, since it only measures the plan's spending, not yours.
Start with the allowed amount, subtract any unmet deductible the patient pays first, then apply the coinsurance split to the rest. For example, on a $1,000 crown with a $100 deductible and 50 percent coinsurance, the patient pays the $100 deductible, then half of the remaining $900, for $550 total, while the plan pays $450, up to the remaining annual maximum.
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