EOB vs ERA (835): what's the difference?

In dental billing, an EOB and an ERA carry the same information—how a claim was adjudicated—but in very different forms.

What is an EOB?

An Explanation of Benefits (EOB) is a human-readable document. It arrives as paper in the mail or a PDF from a payer portal, laid out for a person to read: patient, procedures, billed, allowed, write-off, plan-paid, patient responsibility, denial notes, and the check total. Because it's a document rather than data, someone has to read it and key it in—or run it through EOB extraction.

What is an ERA (835)?

An Electronic Remittance Advice (ERA) is the electronic equivalent, delivered as an ANSI X12 835 file. It's structured data, not a document—designed for software to read directly. When a payer sends an 835, the practice management system can post the payment automatically with no manual reading.

EOB vs ERA at a glance

	EOB	ERA (835)
Format	Document (paper / PDF)	Structured X12 835 file
Audience	Human readers	Software
Posting	Manual, or via extraction	Automatic
Arrives via	Mail, fax, payer portal	Clearinghouse / EDI
Needs reading?	Yes	No

Why do both still exist?

Not every payer sends an 835 for every payment, and not every practice is enrolled for ERA with every carrier. Secondary payers, smaller plans, corrected claims, and certain paper checks still generate EOBs. So even a practice that's fully live on ERAs receives a steady remainder of paper and PDF EOBs—typically a single-digit percentage of payments, but one that never goes fully to zero.

How Pegasus handles both

Argus routes each document to the right path: structured 835 files are parsed deterministically, while paper and PDF EOBs go through AI extraction and exact-math auditing before a human posts them to Open Dental. One workflow, both formats.