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 |
|---|---|---|
| MA26 | Alert: Our records indicate that you were previously informed of this rule. | Details → |
| MA27 | Missing/incomplete/invalid entitlement number or name shown on the claim. | Details → |
| MA27 | Claim/service lacks information or has submission/billing error(s) Missing/incomplet… | Details → |
| MA27 | Missing/incomplete/invalid entitlement number or name shown on the claim. | Details → |
| MA28 | Alert: Receipt of this notice by a physician or supplier who did not accept assignmen… | Details → |
| MA28 | Alert: Receipt of this notice by a physician or supplier who did not accept assignmen… | Details → |
| MA29 | Missing/incomplete/invalid provider name, city, state, or zip code. | Details → |
| MA29 | Missing/incomplete/invalid provider name, city, state, or zip code. | Details → |
| MA30 | Missing/incomplete/invalid type of bill. | Details → |
| MA30 | Missing/incomplete/invalid type of bill. | Details → |
| MA31 | Missing/incomplete/invalid beginning and ending dates of the period billed. | Details → |
| MA31 | Missing/incomplete/invalid beginning and ending dates of the period billed. | Details → |
| MA32 | Missing/incomplete/invalid number of covered days during the billing period. | Details → |
| MA32 | Missing/incomplete/invalid number of covered days during the billing period. | Details → |
| MA33 | Missing/incomplete/invalid non-covered days during the billing period. | Details → |
| MA33 | Missing/incomplete/invalid non-covered days during the billing period. | Details → |
| MA34 | Missing/incomplete/invalid number of coinsurance days during the billing period. | Details → |
| MA34 | Missing/incomplete/invalid number of coinsurance days during the billing period. | Details → |
| MA35 | Missing/incomplete/invalid number of lifetime reserve days. | Details → |
| MA35 | Missing/incomplete/invalid number of lifetime reserve days. | Details → |
| MA36 | Missing/incomplete/invalid patient name. | Details → |
| MA36 | Missing/incomplete/invalid patient name. | Details → |
| MA37 | Missing/incomplete/invalid patient's address. | Details → |
| MA37 | Missing/incomplete/invalid patient's address. | Details → |
| MA38 | Missing/incomplete/invalid birth date. | Details → |
| MA38 | Missing/incomplete/invalid birth date. | Details → |
| MA39 | Missing/incomplete/invalid gender. | Details → |
| MA39 | Missing/incomplete/invalid gender. | Details → |
| MA40 | Missing/incomplete/invalid admission date. | Details → |
| MA40 | Missing/incomplete/invalid admission date. | Details → |
| MA41 | Missing/incomplete/invalid admission type. | Details → |
| MA41 | Missing/incomplete/invalid admission type. | Details → |
| MA42 | Missing/incomplete/invalid admission source. | Details → |
| MA42 | Missing/incomplete/invalid admission source. | Details → |
| MA43 | Missing/incomplete/invalid patient status. | Details → |
| MA43 | Missing/incomplete/invalid patient status. | Details → |
| MA44 | Alert: No appeal rights. Adjudicative decision based on law. | Details → |
| MA44 | Alert: No appeal rights. Adjudicative decision based on law. | Details → |
| MA45 | Alert: As previously advised, a portion or all of your payment is being held in a spe… | Details → |
| MA45 | Alert: As previously advised, a portion or all of your payment is being held in a spe… | Details → |
| MA46 | Alert: The new information was considered but additional payment will not be issued. | Details → |
| MA46 | Alert: The new information was considered but additional payment will not be issued. | Details → |
| MA47 | Our records show you have opted out of Medicare, agreeing with the patient not to bil… | Details → |
| MA47 | Our records show you have opted out of Medicare, agreeing with the patient not to bil… | Details → |
| MA48 | Missing/incomplete/invalid name or address of responsible party or primary payer. | Details → |
| MA48 | Missing/incomplete/invalid name or address of responsible party or primary payer. | Details → |
| MA49 | Missing/incomplete/invalid six-digit provider identifier for home health agency or ho… | Details → |
| MA49 | Missing/incomplete/invalid six-digit provider identifier for home health agency or ho… | Details → |
| MA50 | Missing/incomplete/invalid Investigational Device Exemption number or Clinical Trial … | Details → |
| MA50 | Missing/incomplete/invalid Investigational Device Exemption number or Clinical Trial … | Details → |
| MA51 | Missing/incomplete/invalid CLIA certification number for laboratory services billed b… | Details → |
| MA51 | Missing/incomplete/invalid CLIA certification number for laboratory services billed b… | Details → |
| MA52 | Missing/incomplete/invalid date. | Details → |
| MA52 | Missing/incomplete/invalid date. | Details → |
| MA53 | Missing/incomplete/invalid Competitive Bidding Demonstration Project identification. | Details → |
| MA53 | Missing/incomplete/invalid Competitive Bidding Demonstration Project identification. | Details → |
| MA54 | Physician certification or election consent for hospice care not received timely. | Details → |
| MA54 | Physician certification or election consent for hospice care not received timely. | Details → |
| MA55 | Not covered as patient received medical health care services, automatically revoking … | Details → |
| MA55 | Not covered as patient received medical health care services, automatically revoking … | 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.