Instantly find explanations, causes, and resolution steps for every Claim Adjustment Reason Code (CARC) and Remark Code.
Claim Adjustment Reason Codes (CARC) explain why a payment differs from what was billed. Every 835 ERA and EOB uses these standardized codes.
Search any code or keyword above. Each page includes the full description, common causes, resolution steps, and appeal guidance.
Each denial code page also links to a dedicated Remark Code page — optimized for providers searching for ERA remark code context.
Most denials are reversible. Our guides walk you through the correct steps to correct, resubmit, or formally appeal each denial type.
| Code | Description | View |
|---|---|---|
| 164 | Bilateral 2x The same bilateral procedure code occurs two or more times on the same s… | Details → |
| 164 | Attachment/other documentation referenced on the claim was not received in a timely f… | Details → |
| 164 | Denied. Fifth ICD diagnosis code is invalid for first date of service. | Details → |
| 165 | Bilateral 2xx The same bilateral procedure code occurs two or more times on the same … | Details → |
| 165 | Referral absent or exceeded. Start: 10/31/2004 | Last Modified: 11/01/2017 | Stop: 0… | Details → |
| 165 | Unable to determine referring physician's name and/or provider number. | Details → |
| 166 | Mut Excl The procedure is one of a pair of mutually exclusive procedures in the NCCI … | Details → |
| 166 | These services were submitted after this payers responsibility for processing claims … | Details → |
| 166 | Section of the bill indicating if the old glasses prescription was available was not … | Details → |
| 167 | No Mod The procedure is identified as part of another procedure on the claim coded on… | Details → |
| 167 | This (these) diagnosis(es) is (are) not covered. Usage: Refer to the 835 Healthcare P… | Details → |
| 167 | Denied. Patient status code is missing or invalid for state fund injured workers. | Details → |
| 168 | No Blood A blood transfusion or exchange is coded but no blood product is coded. | Details → |
| 168 | Service(s) have been considered under the patient's medical plan. Benefits are not av… | Details → |
| 168 | Denied. Refraction is not paid when the old prescription is available. | Details → |
| 169 | Obs A 762 (observation) revenue code is used with a HCPCS other than observation (992… | Details → |
| 169 | Alternate benefit has been provided. Start: 06/30/2005 | Last Modified: 09/30/2007 | Details → |
| 169 | Denied. Admitting/Principal ICD diagnosis code is not sufficiently specific. | Details → |
| 170 | HCPCS Req Revenue center requires HCPCS. | Details → |
| 170 | Payment is denied when performed/billed by this type of provider. Usage: Refer to the… | Details → |
| 170 | Denied. Second ICD diagnosis code is not sufficiently specific. | Details → |
| 171 | Comp EM Composite E/M conditions not met for observation and line item. | Details → |
| 171 | Payment is denied when performed/billed by this type of provider in this type of faci… | Details → |
| 171 | Denied. Third ICD diagnosis code is not sufficiently specific. | Details → |
| 172 | Inv Rev Revenue code not recognized by Medicare. | Details → |
| 172 | Payment is adjusted when performed/billed by a provider of this specialty. Usage: Ref… | Details → |
| 172 | Type service/procedure code is missing or is an invalid L&I procedure code. | Details → |
| 173 | No Proc Claim lacks allowed procedure code. | Details → |
| 173 | Service/equipment was not prescribed by a physician. Start: 06/30/2005 | Last Modifi… | Details → |
| 173 | Denied. The admission date and the service dates are incompatible. | Details → |
| 173 | An initial Certificate of Medical Necessity (CMN) or DME Information Form (DIF) was n… | Details → |
| 174 | Service was not prescribed prior to delivery. Start: 06/30/2005 | Last Modified: 09/… | Details → |
| 174 | Denied. L&I did not authorize these services by this provider for this claim. | Details → |
| 175 | Prescription is incomplete. Start: 06/30/2005 | Last Modified: 09/30/2007 | Details → |
| 175 | Service prior to April 1, 1986 must be billed as a separate line item. | Details → |
| 175 | Prescription is not on file or is incomplete or invalid | Details → |
| 176 | Not covered This is not a covered service. | Details → |
| 176 | Prescription is not current. Start: 06/30/2005 | Last Modified: 09/30/2007 | Details → |
| 176 | Denied. Fourth ICD diagnosis code is not sufficiently specific. | Details → |
| 176 | A recent break in medical need 13/15 months have been paid Same and Similar equipme… | Details → |
| 177 | Max Maximum out of Pocket has been reached. Eligible Amounts have been paid at 100%. | Details → |
| 177 | Patient has not met the required eligibility requirements. Start: 06/30/2005 | Last … | Details → |
| 177 | Denied. Fifth ICD diagnosis code is not sufficiently specific. | Details → |
| 178 | Max copay Maximum copay per diem has been satisfied for this benefit period. No copay… | Details → |
| 178 | Patient has not met the required spend down requirements. Start: 06/30/2005 | Last M… | Details → |
| 178 | Denied. First diagnosis code denotes a non-industrial condition or is not sufficientl… | Details → |
| 179 | Cosurgeon Co-Surgeon Not Covered | Details → |
| 179 | Patient has not met the required waiting requirements. Usage: Refer to the 835 Health… | Details → |
| 179 | Admit type is invalid. Valid admit types are 1,2,3, and 4. | Details → |
| 180 | Credit Credit applied for prior RAP payment | Details → |
| 180 | Patient has not met the required residency requirements. Start: 06/30/2005 | Last Mo… | Details → |
| 180 | Denied. Principal procedure date is more than 2 days prior to the bill's first covere… | Details → |
| 181 | MedSurg This service has been down graded to Med/Surg Day | Details → |
| 181 | Procedure code was invalid on the date of service. Start: 06/30/2005 | Last Modified… | Details → |
| 181 | Denied. Principal diagnosis denotes a non-industrial condition or is not sufficiently… | Details → |
| 181 | Procedure code was invalid on the date of service Missing/incomplete/invalid HCPCS | Details → |
| 182 | Skilled This service has been down graded to Skilled Nursing | Details → |
| 182 | Procedure modifier was invalid on the date of service. Start: 06/30/2005 | Last Modi… | Details → |
| 182 | Incorrect revenue code billed for this service. | Details → |
| 182 | Invalid modifier for date of service | Details → |
Medical claim denial codes — formally known as Claim Adjustment Reason Codes (CARC) — are standardized identifiers maintained by the X12 standards body and used across all Medicare, Medicaid, and commercial payer 835 electronic remittance transactions. When a claim is paid at a different amount than billed, at least one CARC code must accompany the remittance advice to indicate the specific reason for the adjustment.
The most frequently encountered codes include CO-16 (missing or invalid claim information), CO-45 (charges exceeding fee schedule), PR-1 (patient deductible), CO-29 (timely filing deadline exceeded), and CO-4 (procedure code inconsistent with modifier). Each represents a distinct, actionable reason that has a defined resolution pathway.