An EOB (Explanation of Benefits) is the human-readable statement of how a claim was processed; an ERA (Electronic Remittance Advice — the X12 835 transaction) is the electronic version posted into your billing system. They convey the same adjudication and carry the same CARC and RARC codes — the ERA is what auto-posts, the EOB is what you read.
What each one is
- EOB — a readable document (paper or PDF) explaining payments, adjustments, and patient responsibility for a claim.
- ERA / 835 — the standardized electronic transaction the payer sends to your clearinghouse/billing system for automatic posting.
- Both reference the same claim and the same adjustment reason codes.
Where the denial codes live
Whether you're reading an EOB or working an ERA, the denial is expressed the same way: a CARC (the adjustment reason, like CO-50 or CO-97) plus, where required, one or more RARCs (remark codes) that add detail. The appeal is built from those codes, not from the format you happen to be looking at.
Frequently asked
Is the 835 the same as the ERA?
Which do I appeal from — the EOB or the ERA?
Primary sources: X12 — Remittance Advice Remark Codes (RARC). General information, not legal or medical advice — confirm against the governing rule for the plan type.
Related guides
When the appeal has to be written, and cited
Upload the denied EOB and Merits returns a complete, citation-verified appeal letter — the clinical argument, the payer's own coverage criteria, and your federal appeal rights — in about a minute.