Denial Radar

Reference playbook

Decode the denial codes most commonly cited in your segment and the angle to appeal each one. Denial rates can only be measured from your own remits, so contribute your 835s (de-identified, on-device) via the Clean Room to see your real breakdown.

Reddenda holds no denial data for your practice. Nothing on this page is your number.

A denial rate cannot be estimated or benchmarked from public data. It can only be measured from your own 835/ERA remits. The playbook below is X12 code reference, identical for every practice in your segment.

Your denial rate

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Not measured. No 835s contributed.

Dollars tied up in denials

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Cannot be inferred. Needs your 835s.

Local-peer denial median

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Not indexed yet. No contributed peer denials.

Measure it: open the 835 Clean Room →

Commonly-cited denial codes in your segmentX12 reference · not your data

Across specialties, the highest-volume denial drivers are authorization, medical necessity, coordination of benefits, and bundling edits. Most are documentation or sequencing problems, which means most are worth working rather than writing off.

CO-197Precert / authorization absent

A required prior authorization, precertification, or notification was not on file.

Prior-auth denials are frequently retro-authorizable inside the payer's window; check the provider manual for the retro-auth exception before appealing.

Appeal angle · Supply the auth number if one existed, or request a retro-authorization with clinical justification and any urgent or emergent exception.

CO-50Not deemed a medical necessity

The payer decided the service was not medically necessary as billed.

Attach the coverage policy or LCD alongside the clinical note; a medical-necessity appeal that cites the payer's own criteria back to it is the one that moves.

Appeal angle · Attach clinical documentation and the applicable coverage policy or LCD showing the service met medical-necessity criteria, and correct any weak diagnosis linkage.

CO-22May be covered by another payer (COB)

Under coordination of benefits, the payer believes another plan is primary.

Verify primary vs secondary and rebill to the correct primary with the EOB attached: usually a resubmission, not an appeal.

Appeal angle · Submit an updated COB record or the primary payer's EOB establishing this payer's correct order of liability.

CO-18Duplicate claim / service

The payer sees this as an exact duplicate of a claim it already received.

A true duplicate is a write-off; a distinct same-day service needs the right modifier and documentation to support it.

Appeal angle · If it is not a true duplicate (different date, site, or units), document the distinction and resubmit; otherwise confirm the original claim's status.

CO-97Bundled into another service

The benefit for this line is included in the allowance for another service that was already adjudicated.

Check the NCCI PTP edit and whether a modifier is genuinely supported by the note. Never append a bypass modifier that the documentation does not earn.

Appeal angle · If the services were separate and distinct, append the appropriate modifier (25, 59, or an X{EPSU} modifier) with documentation showing separately identifiable work.

CO-29Timely-filing limit expired

The claim was received after the payer's timely-filing deadline.

Timely filing: proof of the original, accepted submission (clearinghouse acceptance report) is the only durable appeal.

Appeal angle · Provide proof of timely original submission (clearinghouse acceptance report) or document a valid good-cause exception.

Appeal deadlines are set per payer and per plan: read the denial letter. The clock usually starts at the remit date, not the date of service, and a corrected claim is often faster than a formal appeal.