Common Medical Billing Denial and Rejection Codes Explained (M47, MSP, Entity Code & More)
- Zen Medical Services
- 15 hours ago
- 9 min read
Medical billing denial codes can look confusing, especially when a claim contains several codes from different code sets. Medical billing denial codes explained simply means understanding what each code is telling you, whether the problem is a claim submission error, payer processing issue, eligibility problem, coding issue, or payment adjustment.
One important distinction is that a rejection usually occurs before a claim is adjudicated, while a denial generally means the payer processed the claim but did not approve payment as submitted. Codes such as M47, Medicare Secondary Payer (MSP) indicators, and entity-related rejection codes can point billing teams toward very different corrective actions.
Denial vs. Rejection in Medical Billing
Although the terms are sometimes used interchangeably, they describe different stages of the claims process.
A rejection generally means a claim failed an electronic or administrative validation check. The claim may need to be corrected and resubmitted before the payer can adjudicate it.
A denial generally means the payer has adjudicated the claim or claim line and determined that payment cannot be made, or that payment must be reduced or adjusted.
This distinction matters because the response is different:
Issue | Typical Meaning | Usual Action |
Rejection | Claim contains missing, invalid, or inconsistent information | Correct and resubmit |
Denial | Payer processed the claim but payment was not allowed as submitted | Research, correct, rebill, or appeal |
Adjustment | Payment was changed for a specific reason | Review CARC/RARC and responsibility |
Pending/suspended claim | Payer needs additional processing or information | Monitor and respond as required |
CMS explains that electronic remittance advice reports adjustment reasons at the claim or line level using standardized codes, including Claim Adjustment Group Codes, Claim Adjustment Reason Codes (CARCs), and Remittance Advice Remark Codes (RARCs).
How Claim Adjustment Codes Work
A common mistake is treating every code on an ERA as if it were the same type of denial code.
They are not.
A CARC explains why an adjustment was made. A RARC supplies additional information or clarification. Group codes indicate who is financially responsible for an unpaid amount. For example, CMS identifies CO as Contractual Obligation and PR as Patient Responsibility.
The distinction is important when reviewing claim adjustment reason codes because the same CARC may require different follow-up depending on the accompanying remark code, group code, payer rules, and claim circumstances.
For the authoritative code set, use the CMS Claim Adjustment Reason Codes reference rather than relying on an outdated denial-code list.
M47: Missing or Invalid Payer Claim Control Number
M47 is a Remittance Advice Remark Code, not a CARC by itself. X12 defines M47 as “Missing/incomplete/invalid Payer Claim Control Number.” The payer claim control number can also be called an Internal Control Number (ICN), Claim Control Number (CCN), or Document Control Number (DCN).
M47 is commonly associated with a CARC 16, which indicates that the claim or service lacks information or contains a submission/billing error. The exact correction depends on why the payer expected a claim control number and how the claim was submitted.
Common situations include:
A corrected or replacement claim does not reference the appropriate original claim.
An adjustment is submitted with an incorrect payer claim control number.
The original claim identifier is missing.
The submitted control number does not match the payer's records.
A resubmission is being handled as an adjustment when it should be submitted differently.
How to address M47:
Review the payer's remittance advice.
Locate the original payer claim control number or ICN.
Determine whether the claim is a corrected, replacement, or adjusted claim.
Verify the payer-specific resubmission requirements.
Correct the claim reference information.
Resubmit using the appropriate claim frequency or adjustment process.
Do not assume that simply adding an arbitrary control number will resolve M47. The correct identifier and resubmission method depend on the payer and claim history.
What Does MSP Mean in Medical Billing?
MSP means Medicare Secondary Payer. It refers to situations where Medicare is not the primary payer for a beneficiary's healthcare claim.
An MSP-related issue can occur when the claim does not accurately reflect another payer's responsibility or when Medicare's records indicate that another insurance arrangement should be considered first.
CMS documentation includes specific MSP-related processing rules and adjustments. For example, CMS identifies Medicare Secondary Payer adjustment information within its claims-processing systems and manuals.
Common MSP-related situations may involve:
Employer-sponsored group health coverage
Workers' compensation
Automobile or no-fault insurance
Liability insurance
Certain other coverage situations in which another payer may be primary
CMS's CARC information also includes CARC 22, which indicates that a claim was adjusted because the care may be covered by another payer under coordination of benefits.
How to troubleshoot an MSP issue:
Verify the patient's current insurance information.
Determine whether Medicare or another payer is primary.
Check the patient's Medicare Secondary Payer status when applicable.
Confirm the primary payer's payment information before submitting a secondary claim.
Include the required prior-payer information on the secondary claim.
Review the payer's MSP or coordination-of-benefits requirements.
MSP errors can be more complicated than ordinary demographic corrections because the correct billing order may affect the entire claim.
What Is an Entity Code Rejection?
An entity code rejection generally indicates that an electronic claim transaction has an issue involving the party or entity identified in the claim.
Depending on the transaction and payer, the affected entity may relate to a provider, subscriber, patient, payer, submitter, or another participant in the claim.
X12 claim-status codes include several messages that specifically require an Entity Code. For example, status code 26 means “Entity not found,” while other status codes identify situations such as an entity not being approved or eligible.
Entity-related problems can arise from:
Incorrect provider identifiers
Mismatched provider information
Incorrect payer information
Missing subscriber information
Incorrect patient/subscriber relationships
Provider enrollment problems
Incorrect billing or rendering provider information
Payer-specific EDI requirements
Some claim acknowledgments identify the entity associated with an error. For example, Medicare contractor EDI documentation shows entity identifiers being used alongside claim status information to identify the party associated with a validation issue.
To resolve an entity code rejection, identify the exact entity first. Do not automatically assume the billing provider is responsible. Review the acknowledgment or rejection report, identify the affected entity and claim segment, verify the underlying information, correct the claim, and then resubmit.
Common Rejection and Denial Codes
Billing teams frequently encounter a range of CARCs and RARCs. The following examples are useful starting points:
Code | General Meaning | Typical Follow-Up |
CARC 16 | Claim lacks information or has submission/billing errors | Review accompanying RARC and correct the claim |
CARC 18 | Duplicate claim/service | Confirm whether the service was previously submitted or paid |
CARC 22 | Another payer may be responsible | Verify coordination of benefits and payer order |
CARC 29 | Filing time limit expired | Check timely-filing rules and determine whether an exception or appeal applies |
CARC 47 | Diagnosis is missing, invalid, or not covered | Verify diagnosis coding and payer requirements |
CARC 50 | Service not considered medically necessary by payer | Review documentation, policy requirements, and appeal options |
CARC 62 | Precertification/authorization issue | Verify authorization requirements and submitted authorization data |
CARC 109 | Claim is not covered by this payer/contractor | Confirm payer and submit to the correct destination |
M47 | Missing/incomplete/invalid payer claim control number | Verify the original payer claim identifier and adjustment process |
CMS's code data describes these adjustment reasons, including duplicate claims, coordination-of-benefits issues, timely filing, diagnosis issues, medical necessity, authorization, and incorrect payer routing.
Remember that a CARC should not always be interpreted in isolation. The accompanying RARC and claim details can provide the information needed to determine the correct next step.
How to Read an ERA or EOB
When a payment is posted, start by reviewing the ERA or EOB rather than looking only at the dollar amount.
Look for:
Claim status: Was the claim paid, denied, adjusted, or otherwise processed?
Group code: Who is assigned financial responsibility for the adjustment?
CARC: Why was the claim or service adjusted?
RARC: What additional information does the payer provide?
Claim control number: Which payer identifier is associated with the claim?
Service line: Which specific procedure or service was affected?
Payer message: Does the payer provide a specific correction or appeal instruction?
CMS notes that ERA information can identify adjustments at the claim, line, or provider level.
How to Fix Medical Billing Rejections
A consistent workflow makes rejection management faster and reduces repeat errors.
Step 1: Identify the rejection source.Determine whether the issue came from the clearinghouse, payer, Medicare contractor, or another processing system.
Step 2: Read every associated code.Do not stop at the first code. A CARC may be paired with a RARC that gives the more specific reason.
Step 3: Find the affected field or entity.Check patient demographics, subscriber data, provider identifiers, payer information, authorization data, coding, dates, and claim references.
Step 4: Verify against source records.Use the patient's insurance card, eligibility response, provider enrollment information, authorization record, or original remittance advice as appropriate.
Step 5: Correct the claim.Make only the corrections necessary to resolve the identified problem.
Step 6: Resubmit correctly.Follow the payer's requirements for corrected, replacement, voided, or new claims.
Step 7: Track the outcome.Monitor the resubmitted claim so that another rejection does not remain unresolved.
How to Prevent Recurring Denials
Denial prevention begins before a claim reaches the payer.
Useful controls include:
Eligibility verification before service
Accurate demographic and subscriber data
Provider enrollment and credentialing checks
Authorization verification
Claim-scrubbing edits
Coding and modifier validation
Payer-specific billing rules
Correct claim frequency and resubmission procedures
Timely follow-up on rejected claims
Regular denial trend analysis
A useful approach is to group denials by root cause rather than simply counting individual codes. For example, several different codes may ultimately point to one operational problem, such as inaccurate insurance information or incomplete provider enrollment data.
When to Escalate a Denial
Not every denial should be appealed.
If a claim contains a correctable administrative error, correcting and resubmitting it may be more appropriate. If the payer has made an adjudication decision that conflicts with the medical record, contract, coverage policy, or submitted documentation, an appeal may be appropriate.
Before appealing, confirm:
The payer's appeal deadline
The reason for denial
Whether the issue is correctable
Required documentation
Medical records or supporting evidence
Authorization information
Payer-specific appeal instructions
Document each action so the practice has a clear audit trail.
Denial Management and Revenue Cycle Management
Effective denial management is not simply a back-office task. It is part of the broader revenue cycle.
Practices can use denial trends to identify weaknesses in registration, eligibility, authorization, coding, documentation, claim submission, payment posting, or follow-up.
Zen Services states that its revenue cycle work includes claim processing, eligibility verification, coding compliance, denial identification, accounts receivable follow-up, and reporting.
For practices that need structured support, explore Denial Management & Appeals Services to review how denial management can fit into a broader RCM workflow.
FAQs
What is the difference between a claim denial and a claim rejection?
A rejection generally occurs before the claim completes adjudication because required information is missing, invalid, or inconsistent. A denial generally reflects a payer decision not to pay a claim or service as submitted. The exact terminology can vary by payer and transaction.
What does M47 mean in medical billing?
M47 is a Remittance Advice Remark Code meaning missing, incomplete, or invalid payer claim control number. It can refer to an ICN, CCN, or DCN. It is often used with a CARC such as 16, so both codes should be reviewed together.
Is M47 a denial code or a remark code?
M47 is a RARC, or Remittance Advice Remark Code. It provides additional information about a claim adjustment. It should not be confused with a CARC.
What does MSP mean on a medical claim?
MSP means Medicare Secondary Payer. It refers to situations in which Medicare is not the primary payer for a beneficiary's healthcare services. Billing teams should verify payer order and applicable coordination-of-benefits requirements.
What causes an entity code rejection?
An entity code rejection can occur when a claim identifies a party incorrectly or when required information about a provider, subscriber, payer, patient, or other entity is missing or invalid. The specific entity identifier and claim segment should be reviewed before correcting the claim.
What is CARC 16?
CARC 16 indicates that the claim or service lacks information or contains submission/billing errors. CMS's code data notes that an accompanying remark code is used to provide additional information in applicable situations.
How should a medical billing team handle rejection codes?
First identify the source and exact code combination. Then determine the affected claim field or entity, verify the information, correct the claim, resubmit according to payer rules, and track the result. Recurring codes should be analyzed for root causes.
Where can I verify claim adjustment reason codes?
Use current payer documentation and authoritative code-set resources. CMS provides claim adjustment information, while X12 maintains the CARC and RARC code sets.
Conclusion
Understanding medical billing denial codes explained in plain language can help billing teams move from simply working denial queues to identifying the underlying cause of claim problems.
Codes such as M47, MSP-related adjustments, CARC 16, and entity code rejections each point to different parts of the claims process. The key is to interpret the complete code combination, verify the claim details, correct the actual problem, and monitor the resubmission.
For practices experiencing recurring rejection or denial patterns, a structured denial-management process can help uncover problems earlier and improve the consistency of the revenue cycle.
Ready to identify where your denials are coming from? Get a Free Denial Code Audit from Zen Services.
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