ERA (electronic remittance advice)
An ERA is the HIPAA-standard electronic remittance, the X12 835 transaction (CMS: Payment and Remittance Advice). For each claim line it reports the billed amount, allowed amount, paid amount, and every adjustment as a group code + reason code pair, often with remark codes.
Group codes tell you who absorbs the difference (CMS Claims Processing Manual, Ch. 22):
- CO (contractual obligation): generally a provider write-off, not billed to the patient.
- PR (patient responsibility): may be billed to the patient; deductible, coinsurance, copay.
- OA (other adjustment): used when no other group applies.
ERA enrollment is usually separate from claim enrollment and is set up payer by payer, typically through your clearinghouse. EFT (the deposit itself) is another separate enrollment.
Read ERAs even when the claim "paid": a $0 payment with the whole amount under PR-1 means the deductible absorbed the visit and the patient owes it, and a line paid at fewer units than billed is an underpayment worth checking.