How to read a dental EOB and ERA, line by line

The explanation of benefits tells you what the insurer decided and why, in codes. Read it right and you know, for every dollar, who owes it: the insurer, the patient, or nobody.

The fields that matter

On the EOB	In the 835	What it tells you
Claim number	CLP	The insurer's number for the claim. Use it on every call, letter and appeal.
Procedure billed	SVC	The code and fee you sent. Compare it with the code the insurer paid.
Submitted charge	SVC	Your office fee.
Allowed amount	SVC / AMT	What the insurer says the service is worth under your contract. Check it against your PPO fee schedule.
Deductible, coinsurance	CAS (PR)	The patient's share. PR adjustments are what you may bill the patient.
Contractual write-off	CAS (CO)	The difference between your fee and the allowed amount. You write it off and cannot bill the patient.
Reason and remark codes	CAS, LQ	Why each amount was reduced or denied. Look them up in the denial code library.
Paid	CLP / SVC	What the insurer actually paid on the claim or line.
Provider-level adjustments	PLB	Money taken from or added to the whole payment, often recovering an old overpayment. Easy to miss.
Check or trace number	TRN	Matches the payment to your bank deposit. If no deposit matches, the money never arrived.

The group codes decide who pays

CO, contractual obligation: the office absorbs it. Never bill the patient for a CO amount.
PR, patient responsibility: deductible, coinsurance, or a non-covered service the patient may owe.
OA, other adjustments: often coordination with another plan.
PI, payer-initiated reductions: the insurer reduced it, and the patient generally can't be billed.

The math should add up

For each line: submitted charge − CO adjustments = allowed amount, and allowed amount − PR amounts − other adjustments = paid. When it doesn't add up, something was missed, usually an adjustment on another line or a provider-level adjustment.

Five things to check on every EOB

The paid code is the code you billed. If not, see downcoding.
The allowed amount equals your contracted fee for that code.
Every denied line has a next step and a deadline. See how to appeal.
Provider-level adjustments are explained and tied to a claim.
The payment reached your bank in full, with no card fees taken. See virtual card fees.

Questions

What is the difference between an EOB and an ERA?

An EOB (explanation of benefits) is the paper or PDF version. An ERA (electronic remittance advice, the X12 835 file) carries the same payment details electronically, so software can read it and match it to claims and bank deposits.

What do CO, PR, OA and PI mean on a dental EOB?

They are group codes that say who is responsible for an adjustment. CO is contractual (the office writes it off and cannot bill the patient), PR is patient responsibility, OA is other adjustments, and PI is payer-initiated reductions.

What is a PLB adjustment on an 835?

A provider-level adjustment: money taken from or added to the whole payment rather than one claim, often recovering an earlier overpayment. Check each one, because the claim it relates to may not be in this payment.

Let software read every 835 for you. The free check reads your payment files in your browser, explains every adjustment and flags underpayments and clawbacks.

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General information for dental billing staff, not legal advice. Plan terms, contracts and insurer rules vary: check the patient's plan, your contract and the insurer's provider manual.