Denial Code Decoder
Look up a claim denial code (CARC) or remittance remark code (RARC) and get a plain-language meaning plus a guided, step-by-step path to the right action — fix and resubmit, appeal, or write off.
32 of 32 codes
- CO-45COCharge exceeds the contracted rateDecode
- CO-16COClaim lacks required informationDecode
- CO-18CODuplicate claimDecode
- CO-22COAnother payer is primaryDecode
- CO-29COFiled after the timely filing limitDecode
- CO-50CONot deemed medically necessaryDecode
- CO-97COBundled into another paid serviceDecode
- CO-109COWrong payer for this serviceDecode
- CO-167CODiagnosis not coveredDecode
- CO-197CONo authorization on fileDecode
- CO-288COThe plan required a referralDecode
- CO-286COThe appeal arrived too lateDecode
- CO-96CONot covered — and the group code decides who paysDecode
- CO-55COThe payer calls it unprovenDecode
- CO-236COTwo codes the payer will not pay togetherDecode
- CO-11COThe diagnosis does not support the serviceDecode
- CO-27COCoverage had already endedDecode
- PR-1PRApplied to the deductibleDecode
- PR-2PRApplied to coinsuranceDecode
- PR-3PRCopay amountDecode
- PR-204PRService not covered by the planDecode
- MA130RARCClaim returned as unprocessableDecode
- N265RARCOrdering or referring provider problemDecode
- N290RARCRendering provider identifier problemDecode
- MA27RARCMember entitlement number problemDecode
- M51RARCProcedure code missing or invalidDecode
- N56RARCWrong procedure code for the service billedDecode
- N179RARCPayer asked the member for informationDecode
- N522RARCDuplicate of an already-processed claimDecode
- M77RARCPlace of service is wrong or missingDecode
- MA04RARCThe primary payer's numbers are missingDecode
- N130RARCA pointer, not a reasonDecode
From code to action in under a minute
Every code page explains what the payer is saying in plain language, shows where in the revenue cycle the denial was born, and walks you through the questions a working biller would ask — ending at the action: correct and resubmit, appeal with the right evidence, or write off and fix the leak upstream.
Which lists, which revision, checked when
Code numbers, groups and statuses come from the two code lists X12 publishes and maintains. Every meaning, decision path and prevention note on these pages is written here — the official descriptors are licensed and are never reproduced.
- X12 — Claim Adjustment Reason Codes (opens in a new tab) — list revision dated November 1, 2025, 297 active entries of 407.
- X12 — Remittance Advice Remark Codes (opens in a new tab) — list revision dated July 1, 2026, 1137 active entries of 1216.
Every code published here was checked against those lists on August 7, 2026 and read as active. Re-checking is a scripted step rather than something someone has to remember: the lists are refetched and compared against every code on this page, and a code X12 has since retired fails our build instead of quietly staying up.
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