DENIAL CODE · CO-252

CO-252: Documentation Required to Adjudicate

CO-252 means the claim is pended for documentation, not denied on the merits — the payer needs records or an attachment before it will pay. Pended is not lost, but the clock is running.

Official (X12/WPC): "An attachment/other documentation is required to adjudicate this claim/service."
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Why payers issue CO-252

  • The payer requires medical records or an attachment to process the claim
  • A required attachment wasn't sent with the original claim
  • The service triggers automatic documentation review
  • The RARC specifies exactly what documentation is needed

Is it recoverable? Very recoverable if you move fast — send the requested documentation within the payer's window. The only way to lose it is to miss the deadline.

Common questions

What does CO-252 mean?

CO-252 means the claim is pended for documentation, not denied on the merits — the payer needs records or an attachment before it will pay. Pended is not lost, but the clock is running. An attachment/other documentation is required to adjudicate this claim/service.

How do I appeal or fix a CO-252 denial?

Very recoverable if you move fast — send the requested documentation within the payer's window. The only way to lose it is to miss the deadline. Common causes: the payer requires medical records or an attachment to process the claim; a required attachment wasn't sent with the original claim; the service triggers automatic documentation review; the RARC specifies exactly what documentation is needed.

Is a CO-252 denial worth appealing?

Very recoverable if you move fast — send the requested documentation within the payer's window. The only way to lose it is to miss the deadline. You only pay on what's actually recovered, so there's no cost to working the ones that are winnable.

Other denial codes
CO-197 · Precertification / Authorization Absent →CO-50 · Not Medically Necessary →CO-16 · Missing or Invalid Information →CO-45 · Charge Exceeds Fee Schedule →CO-97 · Bundled into Another Service →CO-29 · Timely Filing Expired →CO-96 · Non-Covered Charge →OA-18 · Duplicate Claim →OA-22 · Coordination of Benefits →CO-11 · Diagnosis Inconsistent with Procedure →CO-151 · Too Many Services (Frequency/MUE) →CO-B7 · Provider Not Eligible →CO-27 · Coverage Terminated →CO-204 · Not Covered Under Current Plan →CO-109 · Not Covered by This Payer →CO-119 · Benefit Maximum Reached →CO-4 · Modifier Inconsistent or Missing →CO-15 · Authorization Number Missing or Invalid →OA-23 · Prior Payer Adjudication Impact →CO-24 · Charges Covered Under Capitation →CO-26 · Expenses Incurred Prior to Coverage →CO-54 · Assistant Surgeon Not Covered →CO-55 · Experimental / Investigational →CO-58 · Inappropriate Place of Service →CO-59 · Multiple/Concurrent Procedure Reduction →CO-107 · Related/Qualifying Claim Not Identified →CO-167 · Diagnosis Not Covered →CO-170 · Denied for This Provider Type →CO-181 · Procedure Code Invalid on Date of Service →CO-182 · Procedure Modifier Invalid on Date of Service →CO-183 · Referring Provider Not Eligible to Refer →CO-185 · Rendering Provider Not Eligible →CO-198 · Precertification / Authorization Exceeded →CO-226 · Requested Provider Information Not Provided →CO-231 · Mutually Exclusive Procedures →CO-234 · Procedure Not Paid Separately →CO-236 · Procedure/Modifier Combination Not Compatible →CO-242 · Out-of-Network / Non-Network Provider →CO-253 · Sequestration Reduction →CO-256 · Not Payable Per Managed-Care Contract →CO-288 · Referral Absent →CO-B15 · Qualifying Service Not Received →CO-B16 · New Patient Qualifications Not Met →CO-A1 · Claim/Service Denied (Remark Required) →

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