Glossary · Billing

Explanation of Benefits (EOB)

An Explanation of Benefits (EOB) is a post-claim summary sent by an insurer to both the patient and provider that details what was billed, what the plan allowed, what the insurer paid, and what the patient owes—it is not a bill.

Verified May 8, 2026 · 5 sources ↓

Drawn from CMSMedicare.govAAPCReginfoMedixrevenuegroup

Definition

Source · Editorial summary grounded in 5 cited references ↓

When an orthopedic practice submits a claim, the payer processes it and issues an EOB to document the adjudication result. The EOB itemizes provider charges (the billed amount), allowed charges (the contractually permitted amount), the insurer's payment, and any patient responsibility remaining after deductibles, co-insurance, or co-pays are applied. A claim number ties the document to the original submission, and remark codes—typically two-to-three alphanumeric characters—explain adjustments, denials, or partial payments at the line-item level.

For orthopedic billing, a single encounter can generate a multi-line EOB: separate line items may appear for the surgical procedure, assistant-surgeon services, implants billed as supplies, and post-operative visits. Each line carries its own allowed-charge calculation, which can differ from billed charges due to fee-schedule caps, bundling edits, or network contract terms. The EOB therefore functions as the primary audit trail linking CPT codes and ICD-10 diagnoses to actual reimbursement.

Providers receive a parallel document called the Electronic Remittance Advice (ERA, 835 transaction), which carries the same financial data in machine-readable form for automated posting. Patients receive a paper or portal-based EOB. The content is nearly identical; the patient-facing version adds a disclaimer that it is not a bill and may include plain-language benefit summaries such as deductible accumulation and out-of-pocket totals.

Why it matters

Misreading or ignoring EOB remark codes is one of the leading causes of unrecovered orthopedic revenue. A CO-96 (non-covered charge) on a total knee arthroplasty implant line, for example, signals a missing or mismatched HCPCS code—a correctable coding error, not a permanent denial. If the practice writes off the balance without reviewing the remark code, the revenue is gone. Conversely, accepting an underpayment that conflicts with the contracted allowed amount constitutes a compliance risk during payer audits. EOBs also establish the clock for timely appeal: most commercial plans allow 90–180 days from the EOB date to file a corrected claim or formal dispute.

Common mistakes

Where people most often go wrong with this concept.

Source · Editorial brief grounded in cited references ↓

Treating the EOB as a bill and collecting patient balances before the actual patient statement is generated, which can result in double-collection complaints.
Failing to reconcile the EOB 'Allowed Charges' line against the contracted fee schedule—accepted underpayments are permanent revenue losses.
Ignoring remark codes on denied or adjusted lines; each code points to a specific, often correctable issue (e.g., missing modifier, authorization not on file).
Confusing the EOB with the ERA (835 transaction): both carry the same financial data, but only the ERA integrates with practice-management software for automated payment posting.
Assuming an EOB with a zero 'Paid by Insurer' amount means the claim was fully denied—it may instead reflect a patient-only responsibility line (e.g., deductible not yet met).
Starting the appeal clock from the date of service rather than the EOB date, which is what most payer contracts specify as the dispute window.

Related codes

Codes commonly involved when this concept appears in practice.

CPT

ICD-10

M17.11 M16.11

Modifiers

59 Distinct procedural service 25 Significant separately identifiable E/M 80 Assistant surgeon AS PA / NP / CNS assistant at surgery KX Medical-policy requirements met

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 5 cited references ↓

01Is an EOB the same as a bill?

No. An EOB explains how the insurer processed the claim and what portion the patient may owe, but the actual bill comes from the provider's billing office as a separate statement. Collecting payment based solely on the EOB before issuing a patient statement is a compliance risk.

02How is an EOB different from an ERA?

Both documents carry the same adjudication data—billed charges, allowed amounts, payer payment, and patient responsibility. The ERA (835 transaction) is the machine-readable version that integrates with practice-management software for automated posting; the EOB is the human-readable version sent to the patient and sometimes the provider as a paper or portal document.

03What should an orthopedic coder do when the EOB 'Allowed Charges' amount is lower than expected?

Compare the allowed amount against the contracted fee schedule for that payer and procedure code. If it falls below the contract rate, initiate a payment dispute within the payer's appeal window—typically specified in your contract from the EOB date. If no contract discrepancy exists, check remark codes for bundling edits or modifier issues that may be correctable via a reconsideration request.

04How long does an orthopedic practice have to appeal a denial shown on an EOB?

Appeal windows vary by payer and are defined in the provider contract, but most commercial plans allow 90–180 days from the EOB date. Medicare has a structured five-level appeals process with specific deadlines starting from the date on the Medicare Summary Notice or ERA.

05What are remark codes on an EOB, and why do they matter for orthopedic billing?

Remark codes are two-to-three character alphanumeric codes that explain why a charge was adjusted, bundled, or denied. In orthopedic billing, common remark codes relate to NCCI bundling of surgical add-on codes, medical necessity mismatches between diagnosis and procedure, and missing implant documentation. Each code points to a specific corrective action, making them the first place to look when a line pays less than expected.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

Mira AI Scribe

Mira flags EOB discrepancies at the line-item level during payment-posting review. When an EOB allowed amount falls below the contracted rate for a given CPT code and payer, Mira marks the line for manual review and surfaces the applicable remark codes alongside the contract benchmark. For surgical encounters where multiple CPT codes are billed on the same date—common in orthopedics—Mira cross-references the EOB's bundling adjustments against NCCI edits to distinguish legitimate bundles from payer-specific denials that may be disputable. If a remark code indicates a missing modifier (e.g., lack of modifier 59 on a distinct procedural service), Mira queues a corrected-claim task with the suggested modifier pre-populated. Mira does not auto-post EOB payments without reconciliation; all lines with a variance between expected and allowed amounts require a coder acknowledgment before the ERA is finalized in the practice-management system.

See Mira's approach

Related terms

Coordination of benefits (COB) Billing

Coordination of benefits (COB) is the process by which two or more health insurance plans divide payment responsibility for a single claim, establishing which plan pays first (primary) and which pays second (secondary) so that combined payments never exceed 100% of the allowed charges.

Prior authorization Billing

Prior authorization (PA) is a payer requirement that a provider obtain approval before delivering a specific service, procedure, or item—otherwise the claim will be denied regardless of medical necessity. Approval is granted when submitted clinical documentation meets the payer's coverage criteria.