The number a dental plan pays has less to do with what you charged than with which fee schedule the plan runs on. UCR, MAC, and the in-network schedule each set a different allowed amount, and mixing them up is how estimates go wrong and balances surprise patients. This guide explains how insurers set the allowed amount, the difference between the three schedules, and exactly where write-offs and patient balances come from.
Last updated July 2026 · Reviewed by the PracticeAlpha billing team
The short answer. Insurers do not pay a percentage of your fee. They pay a percentage of an allowed amount they set, and that allowed amount comes from a fee schedule. UCR (usual, customary, and reasonable) is an area-based allowed amount used mainly out of network. MAC (maximum allowable charge) is a lower fixed schedule on budget plans. The in-network schedule is the contracted rate a participating dentist agrees to accept. Which schedule applies decides how much the plan pays, how much becomes a write-off, and how much the patient owes. Quote the wrong one and the estimate is wrong.
UCR is the amount an insurer treats as an acceptable fee for a procedure, also called the allowed amount. The three words each mean something:
The key point: the plan pays its percentage of the UCR allowed amount, not of your full fee. So an 80 percent plan pays 80 percent of what it allows, which may be less than 80 percent of what you charged. UCR mostly matters for out-of-network care, where there is no contracted rate to fall back on.
Carriers collect fee data by procedure and by geographic area, usually down to the ZIP code, and then set the allowed amount at a percentile of those local fees. That percentile is the lever. A plan set at the 90th percentile allows what 90 percent of local providers charge or less, which is relatively generous. A plan set at the 80th or 70th percentile allows less, so it pays less and leaves more to the patient.
This is why two patients with the "same" out-of-network coverage can owe very different amounts: their plans sit at different percentiles. It is also why a fee that is fully covered under one plan leaves a balance under another. The percentile is invisible on the surface but drives the whole number.
MAC, the maximum allowable charge, is a lower fee schedule some carriers use on cheaper plans, set below both UCR and typical in-network fees. For out-of-network care, a MAC plan can reimburse around half of a UCR allowance, which leaves the patient owing a much larger share. Patients on MAC plans are often surprised by how little the plan pays out of network.
The in-network schedule is different in kind. It is the contracted rate a participating dentist has agreed to accept as payment in full. The patient is not billed above it, and the difference between the dentist's full fee and the contracted rate becomes a write-off. So the three schedules line up from most to least favorable for the patient's balance depending on the situation, and using the wrong one of the three when building an estimate is one of the most common causes of an inaccurate patient quote.
Estimating against the wrong fee schedule is how practices quote patients wrong and misread their own collection rate. We verify the right schedule before treatment so the numbers are real.
See our verification serviceOnce you see the schedules, the money makes sense. Two very different things produce the gap between your fee and what lands in the practice:
Confusing the two distorts everything. Treating a contractual write-off as an underpayment, or missing a legitimate out-of-network balance, both corrupt the practice's real collection rate. And when a plan pays a cheaper alternative than the treatment provided, that is a separate mechanism covered in dental insurance downgrades. For practices that feel their allowed amounts are too low, the schedule itself can sometimes be negotiated, which is the subject of PPO fee negotiation.
UCR stands for usual, customary, and reasonable, and it is the amount an insurer treats as an acceptable fee for a procedure, also called the allowed amount. Usual is the fee the dentist normally charges, customary is the range charged by dentists in the same area, and reasonable accounts for unusual complexity. The plan pays its percentage of that allowed amount, not necessarily of the dentist's full fee.
Carriers collect fee data by procedure and geographic area, usually by ZIP code, and set the allowed amount at a percentile of those fees. A plan set at the 90th percentile allows what 90 percent of local providers charge or less; lower plans use the 80th or 70th percentile. That percentile is a big driver of how much the plan pays and how much the patient is left owing.
MAC stands for maximum allowable charge. It is a lower fee schedule some carriers use on cheaper plans, set below both UCR and typical in-network fees. For out-of-network care, a MAC plan can reimburse around half of a UCR allowance, which leaves the patient owing a much larger share of the bill.
An in-network fee schedule is the contracted rate a participating dentist agrees to accept, and the patient is not billed above it. UCR is the allowed amount used mainly for out-of-network care based on area fee data. MAC is a lower fixed schedule on budget plans. Using the wrong one of the three when estimating is a common source of inaccurate patient quotes.
Two reasons. In network, the difference between the dentist's full fee and the contracted rate is a write-off the patient never sees. Out of network, if the dentist's fee is above the plan's UCR or MAC allowance, the patient can be billed the difference, on top of their normal coinsurance. Knowing which fee schedule applies before treatment is how you quote the patient accurately.
A write-off, or contractual adjustment, is the portion of a dentist's fee that an in-network provider agrees not to collect because it exceeds the contracted fee schedule. It is a normal, agreed reduction, not lost revenue in the way a denial is. Tracking write-offs correctly matters, because confusing a contractual write-off with an underpayment distorts the practice's real collection rate.
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