Patient guide
How Do I Read a Dental EOB? Five Numbers and One Code, Explained Line by Line.
A dental EOB has five numbers that matter: billed, allowed, plan paid, patient responsibility, and the balance. The reason a line was adjusted is a national code, a CARC, maintained by X12, sometimes paired with a RARC that adds detail. Once you can find those, you can check the math yourself.
Reviewed by the CheckMyDenial team, patient billing and appeals. Last reviewed: September 3, 2026.
Short answer: every line of a dental Explanation of Benefits is built from five numbers and one code. The five numbers are the amount billed, the amount allowed, what the plan paid, what you owe, and the balance. The code is why. It is called a Claim Adjustment Reason Code, or CARC, a national standard maintained by X12, the same organization that sets the electronic format your dentist's office uses to file the claim in the first place. Once you know which number is which and where to find the code, you can check the plan's own math instead of taking the bottom line on faith.
See this as a visual walkthrough: If you prefer to see the same steps illustrated in a flipbook format with diagrams, check the illustrated guide. Same content, visual style.
An EOB is not a bill. It is the plan's accounting of what happened to your claim: what was billed, what the plan's contract or fee schedule allows for that procedure, what portion the plan paid, and what portion, if any, landed on you. Most of the confusion patients run into is not about the dollar amounts. It is that the EOB explains an adjustment with a two or three character code instead of a sentence, and most people have never been told where to look that code up.
| Column on the EOB | What it means | Where the number comes from |
|---|---|---|
| Billed amount | What the dental office charged for the procedure | The office's fee for that code |
| Allowed amount | What the plan's contract or fee schedule recognizes as the procedure's value | The plan's network contract, or its fee schedule if out of network |
| Plan paid | The plan's share of the allowed amount | Allowed amount, minus your deductible and coinsurance |
| Patient responsibility | What you owe | Deductible, coinsurance, copay, or non-covered amounts, per line |
| Adjustment code (CARC, sometimes with a RARC) | Why the plan paid less than billed | X12's national Claim Adjustment Reason Code and Remittance Advice Remark Code lists |
What is the difference between the billed amount and the allowed amount?
The billed amount is the dental office's stated fee for the procedure, the number on the original claim. The allowed amount is different: it is what your plan recognizes as the procedure's covered value, set either by the plan's network contract with that office or, for an out-of-network office, by the plan's own fee schedule. The plan calculates your deductible, your coinsurance, and its own payment from the allowed amount, not the billed amount. When a dentist is in your plan's network, the office has agreed to accept the allowed amount as full payment, and the gap between billed and allowed is written off, not billed to you. When the office is out of network, that gap can become your responsibility, which is the single biggest reason two people with the same procedure and the same plan can owe very different amounts.
What are CARC codes, and who decides what they mean?
A Claim Adjustment Reason Code, CARC, is a national code that answers one question: why was this line paid differently than it was billed. CARCs are not invented by your dental plan. They are maintained by X12, an American National Standards Institute-accredited body that has governed electronic healthcare transaction standards for more than four decades, and they are published as an official code set used across the entire industry, on the same electronic remittance format your dentist's billing software reads. Some of the most common ones on a dental EOB: code 1 for a deductible amount, code 2 for coinsurance, code 3 for a copayment, code 96 for a non-covered charge, code 50 when a service is not deemed medically necessary, and code 119 when a benefit maximum for the period has already been reached. The code, not the dollar figure, is the actual reason.
What are RARC codes, and how are they different from CARCs?
A Remittance Advice Remark Code, RARC, adds detail that a CARC alone does not carry, and it is also maintained by X12. There are two kinds. A supplemental RARC clarifies an adjustment that a CARC already flagged, for example specifying that an x-ray was not taken within the required window before the procedure. An alert RARC is informational and is not tied to a specific dollar adjustment at all, such as a note about your appeal rights. When your EOB shows a CARC and a RARC together on the same line, the RARC is frequently the more specific, more useful half of the explanation, and it is the one worth quoting back to the plan if you call to ask questions.
What do the CO, PR, and OA group codes mean?
In front of the CARC number, a dental EOB or remittance carries a group code that tells you whose column the adjustment belongs in. CO means contractual obligation, a reduction the dental office agreed to as part of its network contract, and it generally cannot be passed on to you. PR means patient responsibility, money you owe: your deductible, your coinsurance, your copay. OA means other adjustment, a catch-all category for reductions that are not contractual and not your responsibility in the usual sense. Reading the group code first tells you, before you even get to the number, which side of the ledger a given adjustment sits on.
How do I check the math on my own EOB?
Pull one line. Start with the billed amount, subtract the difference to the allowed amount (that gap, on an in-network claim, should carry a CO code, since it is the office's contractual write-off). From the allowed amount, subtract what the plan paid. What is left should equal your patient responsibility, and every dollar of that gap should trace to a PR-coded line: your deductible, your coinsurance, or a specific non-covered item. If the numbers do not add up, or a CARC on your EOB does not match anything you can connect to your actual treatment or your actual plan terms, that mismatch is worth a phone call, and it is worth putting in writing.
What should I do if a code does not make sense?
Call the number on the EOB and ask the plan two direct questions: what does this specific CARC, and any paired RARC, mean for this specific line, and can you send that explanation to me in writing. Plans are the source of the determination, and they owe you a plain-language answer, not just a code. You can also check the codes yourself against X12's published lists to see the code's general definition before you call, so you know what you are asking about.
A note on who we are
CheckMyDenial helps patients read and appeal insurance denials. We are related to a company that does medical-dental billing and reimbursement for patients and practices, and if you ever move from reading to having someone handle a claim for you, that relationship and any fee are disclosed before anything is paid. This page is free, it does not require anything from you, and it will stay that way.
Where this comes from
The code definitions and the description of how CARC and RARC codes work are drawn from X12's own published code lists, Claim Adjustment Reason Codes and Remittance Advice Remark Codes, the national standards body that maintains both under its accreditation from the American National Standards Institute. The billed, allowed, plan-paid, and patient-responsibility structure reflects how these codes are applied on a standard remittance and EOB. If you find something here that is out of date, tell us and we will fix it and change the date at the top.
Questions people ask
How do I read a dental EOB?
Follow one line of a dental Explanation of Benefits across five numbers: the amount billed, the amount the plan allows for that procedure, what the plan paid, what you owe, and a code explaining any adjustment. The code, usually two or three characters, is a Claim Adjustment Reason Code, a national standard maintained by X12. Look up that code to find out exactly why the plan paid less than it billed, rather than guessing from the dollar amounts alone.
What is the difference between the billed amount and the allowed amount on a dental EOB?
The billed amount is what the office charged. The allowed amount is what your plan's contract with that office, or its fee schedule if out of network, says the procedure is worth. The plan pays its share of the allowed amount, not the billed amount. An in-network office writes off the gap between billed and allowed, and cannot bill you for it. Out of network, that gap can become your responsibility, which is why network status matters as much as the dollar figures.
What is a CARC code on a dental EOB?
CARC stands for Claim Adjustment Reason Code, a national code set maintained by X12, the same standards body that governs the electronic claim format your dentist's office uses to bill. Every line on your EOB that was paid differently than it was billed carries at least one CARC explaining why: a deductible, a coinsurance amount, a non-covered service, or dozens of other specific reasons. The code is the actual reason. The dollar figure is just the result of it.
What is a RARC code and how is it different from a CARC?
A RARC, Remittance Advice Remark Code, adds detail a CARC alone does not carry. Where a CARC might say a service was not covered, a paired RARC can specify why, for example that an x-ray was not taken within the required time window. RARCs are also maintained by X12. When an EOB shows both a CARC and a RARC on the same line, read them together; the RARC is often the more specific, more actionable half of the explanation.
What do the group codes CO, PR, and OA mean on an EOB?
These claim adjustment group codes tell you who is responsible for an adjustment. CO means contractual obligation, an amount the office wrote off under its contract with the plan, and you generally cannot be billed for it. PR means patient responsibility: a deductible, a coinsurance amount, money you owe. OA means other adjustment, a catch-all for reductions outside the first two categories. The group code in front of a CARC number tells you, at a glance, whose column that dollar figure belongs in.
Why does my dental EOB show a different amount than what I was billed at the office?
Most often because the office billed its full fee, and the EOB reflects what the plan actually allows and pays after applying the allowed amount, your deductible, your coinsurance, and any plan-specific limits like an annual maximum or a downgrade. Each adjustment carries its own CARC. Add up every reduction and the codes attached to them and the final patient-responsibility number should reconcile with what you are asked to pay.
What should I do if I do not understand a code on my EOB?
Call the number on the EOB and ask the plan to state, in plain language, what each CARC and RARC on the denied or reduced line means for your specific claim, and ask them to send that explanation in writing. You can also look up the code definitions yourself using the national CARC and RARC lists published by X12. If the explanation does not match your actual treatment or plan terms, that mismatch is the starting point of an appeal.