Denial Code Lookup
Type a denial code from your remittance — CO-45, CO-97, CO-197 — or a keyword like 'duplicate' or 'authorization', and get what it means, why it happened, and the fix, straight from our denial library.
A denial code is a sentence compressed into a label — and every biller loses time decompressing it. This lookup covers the claim adjustment reason codes (CARCs) that appear most often on remittances, with the three things you actually need: what the code means, the usual cause behind it, and the fix that gets the claim paid. For the full narrative treatment, see our complete denial codes guide.
Look up a denial code
First, read the group code
Every adjustment starts with a group code that says whose money it is — read it before the reason code:
- CO (Contractual Obligation) — the provider absorbs it; CO amounts generally cannot be billed to the patient.
- PR (Patient Responsibility) — deductible, coinsurance, copay. Not a true denial: bill the patient.
- OA (Other Adjustments) — coordination-of-benefits and prior-payer effects live here.
- PI (Payer Initiated Reductions) — reductions that are neither contract nor patient responsibility.
Then work the fix, not just the claim
Single claims get corrected one at a time, but codes repeat for reasons: the same CO-197 means authorizations are being missed at scheduling; repeated CO-16s mean a field or attachment is systematically absent. Practices that trend their top codes monthly — the routine behind our denial management work — watch whole families disappear. To see what your current denial pattern costs per year, run the denial cost calculator; when a denial is wrong rather than fixable, our appeal guide walks the escalation.
Frequently asked questions
What is the difference between a CARC and a RARC?
The CARC (Claim Adjustment Reason Code) gives the headline reason a claim or line was adjusted or denied — pricing, bundling, authorization, filing. The RARC (Remittance Advice Remark Code) adds the detail, often naming the exact missing item or rule. Read them together: the CARC says what family the problem is in, the RARC usually says precisely what to fix.
Is CO-45 a denial I should appeal?
No. CO-45 is the standard contractual adjustment between your billed charge and the contracted allowable — it appears on almost every paid claim. It is written off, never appealed, and never billed to the patient. If the allowable itself looks lower than your contract rate, that is an underpayment issue, not a CO-45 issue.
Which denial codes are worth appealing instead of correcting?
Codes where the payer's position is wrong or incomplete: CO-50 medical-necessity denials with strong documentation, CO-29 when you hold proof of timely filing, CO-151 when notes support the units billed, and bundling denials (CO-97/CO-234) when documentation proves a distinct service. Error codes like CO-16 or CO-31 are corrected and resubmitted instead.