Notes on payer behavior
What an 835 actually tells you (and what your posting software throws away)
An 835 is the electronic remittance advice: the HIPAA-standard file (ASC X12N 005010X221A1) an insurer sends to explain how it paid, reduced, or denied each claim, line by line. It's the machine-readable version of the paper EOB, and it is the single richest record of payer behavior your practice owns. It's also the record most practices never look at directly, because posting software reads the few fields it needs to close a balance and discards the rest. The discarded part is where underpayment lives.
What's in the file
Strip away the EDI syntax and an 835 has four layers.
| Layer | Segment | What it carries | Why you care |
|---|---|---|---|
| Payment | BPR, TRN | The check or EFT amount, date, and trace number | Ties the file to the deposit in your bank |
| Claim | CLP | Claim number, status code, billed charge, paid amount, patient responsibility | Status 1 to 3 = processed; 4 = denied; 22 = reversal of a prior payment |
| Service line | SVC, CAS, AMT, DTM | The code paid, the code submitted when it differs, line charge, line paid, allowed amount, each adjustment with a group code, reason code, and amount, dates of service | This is where a downcode, a bundling edit, and a short allowed amount are recorded |
| Provider level | PLB | Adjustments applied to the whole payment rather than a claim: recoupments, offsets, interest, penalties | Money taken back that never appears on any claim line |
The five fields that reveal underpayment
- The submitted procedure code (SVC06). When the payer changes your code, the original goes in this field. Your software posts the paid code (SVC01). If they differ, you were downcoded or recoded, and the line looks clean. Downcoding, explained.
- The allowed amount (AMT with qualifier B6). This is the payer's assertion of your contract rate. It's the number to compare against your fee schedule. Paid amount tells you about the patient's deductible; allowed tells you whether the contract was honored.
- The adjustment group and reason codes (CAS). CO means contractual, your write-off. PR means patient responsibility. OA means other. Each comes with a reason code from the X12 CARC list: 45 for fee schedule, 97 for bundling, 150 for level of service, 197 for authorization, 29 for timely filing. A CO adjustment is the payer telling you what you agreed to. It's often right. It's worth checking.
- The remark codes (LQ / RARC). The reason code says what; the remark code often says why, and sometimes names the policy. CO-16 is unreadable without them.
- The provider-level adjustments (PLB). Recoupments for "overpayments" identified months later, offsets against unrelated claims, and, on Florida fully insured plans, the 12 percent prompt-pay interest you're owed. Posting software routinely dumps PLB amounts into an unapplied bucket. That bucket is worth a quarterly look.
What posting throws away
A typical practice management system reads CLP and SVC, posts paid and adjustment amounts, closes the balance, and moves on. It usually does not store the submitted code alongside the paid code, does not compare allowed to contract, does not report by CARC across payers, and treats PLB as an accounting exception. None of that is a flaw for its purpose. Its purpose is to post. Reading payer behavior is a different purpose and needs the raw file.
How to get your 835s
- Your clearinghouse. Every 835 it delivered is downloadable, typically for at least a year. Ask for the raw files, not the human-readable report.
- Payer portals. Availity and the payer-specific portals let you pull remittances by check date. Useful for the payers that bypass your clearinghouse.
- Your billing company. If they post for you, the files pass through them. They're your records; ask for the archive.
Keep twelve months at minimum. Florida's underpayment window on state-regulated plans is 12 months from the payment date, and a file you don't have is a claim you can't make.
Three checks you can run in a spreadsheet
- Submitted code versus paid code across your top ten visit and procedure codes. Count the mismatches by payer.
- Allowed amount versus contract for your top twenty codes, by payer. Flag any line where allowed is below the fee schedule. Sum by payer.
- CAS reason codes by payer by month. A payer whose CO-97 or CO-150 count doubles in a quarter changed a rule. That's a pattern, and patterns are what get reversed.
Each takes an hour once the files are in one place. The first time most practices do this, the allowed-versus-contract check alone finds a number that justifies the afternoon.
What it means for your practice
You already own the evidence. It arrives every week, in a format designed to be machine-read, and it records exactly what each insurer did to each line. The only question is whether anyone reads it for something other than posting. That read, across every line of a year, is what Clearia's diagnostic is. It costs nothing, and it starts with the files you already have.