To read an EOB, start at the header to identify the payer and the payment, match the claim block to the claim you sent, then read each service line left to right: billed charge, allowed amount, adjustments, patient share and plan payment. The codes printed beside each line explain every difference between billed and paid.
What does the EOB header tell you about the payer and the payment?
The header of an explanation of benefits (EOB) names the health plan that processed the claim and, on a provider copy, the payment it describes. An EOB is the plan's statement of how it decided a claim. The CMS guide to the explanation of benefits says plainly that an explanation of benefits isn't a bill.
The header usually holds four groups of facts. The payer block gives the plan's name, address and phone number. The payee block names who receives the money, which on a provider EOB is the practice or billing entity. The payment block shows a check number or an electronic funds transfer (EFT) trace number with its date and total. The document block carries the date the EOB was produced and, on multi-page EOBs, a page count.
The payment number is the key a billing team uses most. A deposit on the bank statement, the EOB and the payment posting in the practice management system should all carry the same check or EFT number and the same total. When the three disagree, the EOB header is the first place to look, because one payment often covers many claims and many patients.
Member EOBs, the copy a patient receives, usually leave out the check number and show the plan's member services phone number instead. The CMS guide lists the payee, the plan's phone number and a claim number among the facts an EOB shows about the patient and the plan. The differences between the provider and member copies matter enough to have their own section at the end of this post.
Reading the EOB claim block: patient, claim number and service dates
The claim block ties a group of service lines to one claim. It names the patient and usually the subscriber, shows the member ID, gives the payer's claim number, and lists the dates of service. On a provider EOB it may also show the provider's own account or patient control number that was sent on the claim.
Matching the claim block to the claim you sent is the first check. Use the patient control number when the EOB prints it, because it is the number your system assigned. When it is missing, match on patient name, member ID and date of service together. A name alone is not enough: plans abbreviate and truncate names, and two family members can share a subscriber ID with different suffixes.
The payer's claim number is the reference you quote on a call or an appeal. It is assigned by the plan, so it will not match anything in your system until you record it. Billing teams usually store it against the claim when they post the payment, so a later question about the claim starts from the plan's own reference.
Service dates deserve a second look. A claim that spans several days, such as a series of therapy visits, may print one date range in the claim block and individual dates on each service line. If a line's date falls outside the claim's range, the plan may have split or combined claims, and the totals will not match what you billed.
EOB service line columns from billed to paid
Each service line on an EOB follows one procedure from what the provider charged to what the plan paid. Read the columns left to right. The CMS guide names the core ones: provider charges, allowed charges, paid by insurer, and what you owe, plus a remark code that explains costs, charges or payments.
The exact labels vary by payer, so it helps to know the job each column does rather than its name:
| Column job | Common labels | What it holds |
|---|---|---|
| Service | Procedure, CPT/HCPCS, description | The code and a short description of what was done |
| Date | Date of service | When this line's service happened |
| Billed | Provider charges, amount billed, charges | What the provider submitted for this line |
| Allowed | Allowed charges, allowed amount, eligible | The amount the plan recognizes for this service |
| Adjustment | Not covered, discount, contractual adjustment | The difference between billed and allowed, with a code |
| Patient share | Deductible, coinsurance, copay, what you owe | What the plan assigns to the patient |
| Plan payment | Paid by insurer, plan paid, payment | What the plan pays on this line |
| Codes | Remark, reason, adjustment codes | Short codes that explain the line |
Most lines obey one piece of arithmetic: billed minus adjustments equals allowed, and allowed minus the patient share equals the plan payment. When a line does not add up, a code on that line explains why.
The meaning of the allowed amount and how the patient share is split between deductible, coinsurance and copay belongs to its own post. The guide to allowed amount on an EOB as the contracted rate walks through that math line by line.
One service line, worked
This fictional example follows a single office-visit line. Every value is made up for the example.
| Column | Example value | How it is reached |
|---|---|---|
| Billed | $250.00 | The practice's charge for the visit |
| Contractual adjustment (CO-45) | $90.00 | The charge above the contracted rate |
| Allowed | $160.00 | $250.00 billed minus the $90.00 adjustment |
| Deductible (PR-1) | $40.00 | The patient's remaining deductible |
| Coinsurance (PR-2) | $24.00 | 20% of the $120.00 left after the deductible |
| Patient share | $64.00 | $40.00 plus $24.00 |
| Plan payment | $96.00 | $160.00 allowed minus the $64.00 patient share |
Read this way, the line is fully explained: $90 written off under the contract, $64 billed to the patient, $96 paid by the plan, which together equal the $250 charge.
Where do adjustment codes sit on an EOB page?
Adjustment codes appear in one of two places: in a codes column on the service line itself, or as a short reference on the line that points to a glossary at the bottom of the page or the end of the EOB. Either way, each code explains one adjustment on one line.
On provider EOBs the codes usually come in pairs. A group code says who carries the adjustment, and a reason code says why. The X12 Claim Adjustment Reason Codes list describes these codes as explaining "why a claim or service line was paid differently than it was billed". What each group code means for who absorbs the amount is covered in the guide to what the CO, PR, OI and PI group codes mean.
The worked line above uses three such pairs from that list. CO-45 marks a charge that exceeds the fee schedule or contracted arrangement. PR-1 is a deductible amount and PR-2 a coinsurance amount. On a paper EOB, these pairs usually print in the codes column of the line they explain.
Remark codes are a separate set. They add information about how a line was processed rather than naming the reason for an adjustment. A member EOB often prints only remark codes, in the payer's own short format. The CMS guide describes a remark code as a note from the plan, usually two or three letters and numbers, with a description of each code at the bottom of the EOB.
The reason codes billing teams meet most often have their own post, the guide to the CARCs billing teams see most often. This section covers where the codes sit, not what each one means.
EOB page totals and the check summary
Page totals add up the service lines on each page, and the check summary adds up every claim the payment covers. Both use the same columns as the service lines: billed, allowed, adjustments, patient share and paid. The paid total on the last page should equal the check or EFT amount in the header.
Reconciling a multi-page EOB is a matter of summing in order. Add each claim's lines and compare with that claim's subtotal. Add the claim subtotals and compare with the page total. Add the page totals and compare with the check summary. A difference at any step points to a specific claim or page instead of the whole document.
Two kinds of amounts break the simple sum. Provider-level adjustments, such as recoupment of an earlier overpayment or an interest payment, change the check amount without belonging to any claim on the EOB. They usually print in a separate section near the summary. If the claim totals add up but the check does not, look there before you assume a line is wrong.
The second is a zero-pay claim. A claim the plan denied in full still appears on the EOB with its lines and codes, and its billed amount still counts in the billed total. Its paid amount is zero, so it narrows the gap between billed and paid without adding to the check.
Keying these totals by hand is where many posting errors start. Schema Care reads EOB service lines, allowed amounts, plan payments and remark codes into structured fields, scores its confidence in each one, and sends the fields it is unsure of to a person, which you can see on the fictional EOB in the threshold demo.
Dental EOB differences: tooth numbers, frequency limits and alternate benefits
A dental EOB uses the same header, claim block and service-line arithmetic as a medical EOB, but its lines carry extra fields. Each line can name a tooth number or area of the mouth and a tooth surface, and its codes often refer to plan limits and alternate benefits that medical EOBs rarely show.
Tooth and surface fields come from the dental claim. The ADA page on the ADA Dental Claim Form describes completion instructions that say, by CDT code, when the area of the oral cavity, tooth numbers or tooth surfaces should be reported, and it names the universal tooth numbering system as the one used on the form. Those fields matter when you match a line to the claim. Two identical procedure codes on the same date are not duplicates if they apply to different teeth. A matching check that ignores the tooth column will flag them as one service billed twice.
Frequency limits are a common dental-specific explanation. The ADA glossary of dental terms defines limitations as restrictive conditions in a dental benefit contract, such as age, length of time covered and waiting periods. A plan that covers a cleaning or a set of X-rays only a set number of times in a period will show a line over that count with a zero payment and a code pointing to the limit.
Alternate benefit lines are the other pattern to recognize. The same ADA glossary defines an alternate benefit as a plan provision that lets the payer base the benefit on an alternative procedure that is generally less expensive than the one provided. The line then shows an allowed amount lower than the fee for the procedure performed, with a code explaining the substitution, so it is not a keying error.
Provider EOB vs member EOB: reading the wrong copy
A provider EOB and a member EOB describe the same claim decision, but they are written for different readers, and their numbers can look like they disagree. The provider copy groups claims by payment and shows group and reason codes. The member copy shows one patient's claims, plain-language notes and what the patient may owe.
The most common confusion is the patient balance. The CMS guide notes that the member EOB's patient balance does not show whether the patient already paid part of it. A practice that collected a copay at the front desk sees the same amount on its own ledger as paid, while the member EOB still lists it as owed.
The second is timing. A member EOB is produced for each processed claim, while a provider EOB covers a payment run. A patient may receive an EOB for a claim whose payment the practice has not yet received or posted.
The third is scope. When a patient brings in their EOB and asks about a charge, read the claim number and service date before the amounts. A member EOB can cover services from another provider entirely, such as a lab or an imaging center billing separately for the same visit.
Medicare remittances use their own layout and field names on the provider side. The guide to Medicare remittance fields, ICN, MOA codes and reason codes covers that format. For moving paper EOB data into an electronic remittance workflow, read the post on converting a paper EOB to an 835, and for how EOBs fit into the wider billing cycle, the overview of the EOB in medical billing and the claims and medical bills category.