What Is ERA 835 in Medical Billing? How to Read, Post, and Reconcile It

7 min read Medical Billing 2026 Guide

Billing team reviewing an electronic remittance advice on a computer screen, illustrating ERA 835 payment posting

Direct answer: ERA 835 is the electronic remittance advice a payer sends to explain how it handled your claims. ERA stands for Electronic Remittance Advice, and 835 is the ASC X12 transaction format it travels in. For each claim and each service line, the ERA says what was billed, what was allowed, what was paid, what was adjusted, and what was assigned to patient responsibility, with reason codes for every difference. It is the document your billing software reads when it posts payments automatically. If you only watch the bank deposit, you know money arrived. If you read the ERA, you know why that amount is what it is, and what still needs work.

ERA, EOB, AND EFT, KEPT SEPARATE

Three terms get mixed up, and mixing them up causes real posting errors. The ERA is the information: the payer's line-by-line explanation, sent to the provider, usually through a clearinghouse, in the 835 format. The EFT, electronic funds transfer, is the money itself, deposited to the practice bank account. The EOB, explanation of benefits, is typically the member-facing version: the notice a patient receives explaining what the plan paid and what the patient may owe. An EOB is not a bill, and it is not designed for posting. The practical rule is simple: the ERA explains, the EFT pays, the EOB informs the patient. An ERA arriving without a matching deposit, or a deposit arriving without a matching ERA, is an exception that needs follow-up, not a payment you can close out from memory.

HOW AN ERA AND AN EFT ARE MATCHED

The ERA and the EFT travel separately and are paired by a reassociation trace number, the TRN segment carried in both records. Your software or your biller matches the deposit in the bank to the ERA by that trace number, then posts the ERA lines to the open claims. Under the federal standards, the adopted standard for the health care claim payment and advice transaction is the 835, referenced in 45 CFR 162.1602. Payer and clearinghouse rules still vary in detail, so confirm enrollment and format requirements with each payer rather than assuming one payer's setup works for all of them. Also note that an 835 can report a payment by check as well as by EFT, so seeing an 835 does not by itself prove an electronic deposit is on its way. Match the trace number to the bank record before you call a payment received.

WHAT IS INSIDE AN 835, LAYER BY LAYER

An 835 is organized in layers, and reading it top-down keeps posting errors down. At the top is the payment itself: the total amount, the payment date, and the trace number. Beneath that are claim-level records, each identified by the patient control number your practice assigned and the payer's claim number, with a claim status. Beneath each claim are service lines, and each line carries the billed amount, the allowed amount, the paid amount, and adjustments. Every adjustment has three parts that must be read together. The group code says who bears the amount: CO means contractual obligation, a provider write-off under contract, and PR means patient responsibility. The CARC, claim adjustment reason code, says why, for example CO 45 for a contractual adjustment or CO 16 for missing information. An optional RARC, remittance advice remark code, adds detail, such as which document is missing. Reading only the paid amount and skipping the codes is how underpayments hide in plain sight.

WORKED EXAMPLE

A practice bills one service line for $200, an illustrative example, not a real claim. The ERA returns an allowed amount of $140, a paid amount of $110, a CO 45 adjustment of $60, and a PR adjustment of $30 for the patient's deductible. Posted correctly, the line balances like this: billed $200, minus contractual adjustment $60, leaves allowed $140; allowed $140, minus patient responsibility $30, leaves paid $110. The $30 moves to the patient balance only after the deductible is confirmed, and the $60 contractual adjustment is written off under contract, not billed to the patient. If the biller posted only the $110 payment and ignored the codes, the $30 patient balance would never be created and the $60 would sit unexplained in accounts receivable. The arithmetic is the whole job: billed, minus adjustments, must equal paid plus patient responsibility, line by line.

THE POSTING ORDER THAT PREVENTS BACKLOGS

Post in the same order every time. First, match the ERA to its deposit by trace number and confirm the totals agree. Second, auto-post the clean lines, where billed minus adjustments equals paid plus patient responsibility and no code needs a human decision. Third, route every exception to a person the same day: denials, partial payments, patient responsibility that does not match the eligibility check, and any line where the arithmetic does not balance. Fourth, move patient responsibility to the patient account only after the eligibility and contract checks confirm it belongs there, not on the strength of a PR code alone. Fifth, reconcile: the ERA total, the deposit total, and the posted total must agree, and any difference must be logged with a reason, not forced to balance. A payment is not finished when it is posted. It is finished when it is posted, balanced, and every exception has an owner and a next step.

COMMON POSTING ERRORS AND THEIR FIXES

The most common errors are easy to name and easy to prevent. Posting the paid amount without reading the adjustment codes, which hides underpayments and misroutes patient balances. Posting a paper remittance by hand without a second check, where transposition errors creep in. Treating a PR code as automatic permission to bill the patient, when the contract, the payer's rules, and state rules may say otherwise. Letting exceptions sit in a queue with no owner, so a denial ages past its appeal window while everyone assumes someone else is working it. And closing a payment when the deposit and the ERA disagree, which guarantees a reconciliation difference at month end. The fix for all five is the same discipline: read the codes, balance every line, assign every exception, and reconcile every batch before moving on.

ERA POSTING CHECKLIST

ERA matched to its deposit by trace number.
Totals agreed before posting.
Clean lines auto-posted, exceptions routed the same day.
Group code, CARC, and RARC read together on every adjustment.
Patient responsibility confirmed before billing the patient.
Denials worked through their own routes, not reposted unchanged.
Batch reconciled: ERA total, deposit total, and posted total in agreement, differences logged with reasons.

FREQUENTLY ASKED QUESTIONS

What does ERA stand for? Electronic Remittance Advice, the payer's electronic explanation of how claims were processed.

What is the difference between an ERA and an EOB? An ERA is the provider-facing 835 file used for posting. An EOB is typically the patient-facing explanation of benefits, and it is not a bill.

What is the difference between an ERA and an EFT? The ERA explains the payment. The EFT is the money, deposited to the bank. They are matched by a trace number.

Does an ERA mean the claim is fully paid? No. It means the payer adjudicated it. Read the codes: part of the line may be adjusted, denied, or assigned to patient responsibility.

What should I do if the deposit and the ERA do not match? Do not force them to balance. Follow up with the payer or clearinghouse, log the difference, and keep the batch open until it reconciles.

Can an ERA be posted by hand? Yes, but a paper remittance must be keyed carefully and checked, because hand posting is where transposition errors happen.

A note on codes and rules: CARC descriptions are summarised from the official X12 code lists and common payer usage. Payer enrollment, format, and timing rules vary, so always confirm a code and a payer's rules against the official lists and the payer's own guidance before acting. This article is educational information about billing workflows, not legal or compliance advice.

Need help turning remittances into clean, reconciled postings? Neximed Billing provides payment posting, denial management, and accounts receivable support. Contact us at info@neximedbilling.com or +1-406-2251570.