CurrentUnitedHealthcarePolicy 2025R5034A

Unacceptable Principal and Inappropriate Primary ICD-10-CM Diagnosis Codes for CMS-1500/UB-04 Claims

Defines diagnosis coding requirements and lists diagnosis codes that are unacceptable as principal (inpatient) or inappropriate as primary (outpatient/professional) for reimbursement of claims billed on CMS-1500 and UB-04 forms; applies to UnitedHealthcare Commercial and Individual Exchange claim submissions and providers submitting those claims.

Policy Summary

PayerUnitedHealthcare

PolicyUnacceptable Principal and Inappropriate Primary ICD-10-CM Diagnosis Codes for CMS-1500/UB-04 Claims

Policy CodePolicy 2025R5034A

Change TypeRevised code lists

Effective Date

Next Review Date

Key ActionSubmit accurate claims with appropriate procedure and diagnosis codes in accordance with CPT/CMS and ICD-10-CM guidelines.

SourceLink

POLICY UPDATE CHANGES

Updated codes for Unacceptable Principal and Inappropriate Primary ICD-10-CM Diagnosis Codes List.

MS-DRG 998DRG representing invalid principal diagnosis

CMS-1500 & UB-04claim form types governed

Multiplepolicy history entries updating code lists

Coverage Criteria for Diagnosis Coding

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Coverage criteria for diagnosis coding

Claims will be evaluated for reimbursement based on appropriate principal/primary diagnosis coding; specific lists identify unacceptable or inappropriate diagnosis codes and rules for evaluation.

Coverage criteria for diagnosis coding

ALL of the following

Inpatient UB-04 claims: The principal diagnosis (Box 67 on the UB-04 or electronic equivalent) must NOT be selected from the 'Unacceptable Principal ICD-10-CM Diagnosis Codes List'. Claims with a principal diagnosis on that list will be denied (entire claim denial).
Applies to inpatient claims submitted on a UB-04 claim form.
DRG 998: Diagnoses that represent a discharge reporting a principal diagnosis invalid as a principal diagnosis (MS-DRG 998) are included in the unacceptable principal diagnosis guidance; examples include unspecified diabetes mellitus or unspecified genitourinary infection in pregnancy when insufficient to determine principal diagnosis.
MS-DRG 998 references the classification of invalid principal diagnoses.

ALL of the following

Outpatient UB-04 and Professional CMS-1500 claims: Codes listed on the 'Inappropriate Primary ICD-10-CM Diagnosis Codes List' should not be used as the primary/first‑listed diagnosis. If an inappropriate diagnosis code is linked as primary in box 24E on a CMS-1500 and the claim has multiple lines, only the claim line(s) associated with that inappropriate primary diagnosis will be denied; other lines may be paid.

ALL of the following

Claims must include an appropriate diagnosis coded and submitted in accordance with the official ICD-10-CM Guidelines for Coding and Reporting. Manifestation codes, 'code first' notes, sequela and transplant complication coding, external cause codes, Z codes and Excludes1 rules must be followed when sequencing and reporting diagnosis codes.

ALL of the following

Submit accurate claims with appropriate procedure and diagnosis codes; follow CPT/CMS and other coding guidelines referenced by UnitedHealthcare. Providers are responsible for correct submission of claims.

ALL of the following

Denial behavior: If an inappropriate principal diagnosis is submitted in Box 67 of the UB-04, the entire claim will be denied. If an inappropriate diagnosis is linked as primary on a CMS-1500 with multiple lines, only the lines associated with that diagnosis will be denied.

Unacceptable / Inappropriate Diagnosis Codes and Coding Rules

Unacceptable Principal ICD-10-CM Diagnosis Codes (DRG 998)mixedNot Covered

MS-DRG 998

Represents a discharge reporting a principal diagnosis that is invalid as a principal diagnosis.

ICD-10-CM coding adherence

RequirementDiagnosis must be coded and submitted in accordance with the official ICD-10-CM Guidelines for Coding and Reporting to be considered for reimbursement.

ScopeApplies to coding submitted on CMS-1500 and UB-04 claim forms (principal/primary diagnosis placement must follow form-specific instructions).

Guidance referenceConsult the ICD-10-CM Official Guidelines for detailed descriptions of coding rules referenced by this policy.

Examples of applicable rulesIncludes manifestation codes, 'code first' sequencing, sequela coding, transplant complications, external cause (V00-Y99), Z codes use, sepsis category (R65), and Excludes1 rules.

Provider Responsibilities and Claim Handling

Documentation Required

Submit accurate claims with correct procedure and diagnosis codes

You are responsible for submission of accurate claims. Submit claims with the procedure and diagnosis codes that correctly describe the services provided and follow CPT, CMS, or other coding guidelines referenced by UnitedHealthcare.

Include the appropriate principal or primary diagnosis code in the correct claim form field (UB-04 Box 67 for inpatient; CMS-1500 Box 24E diagnosis pointer for professional claims).
Follow official ICD-10-CM Guidelines for Coding and Reporting and any CPT/CMS coding guidance referenced by UnitedHealthcare.

Denial Risk

Denial behavior depends on claim form and diagnosis placement

If an inappropriate diagnosis is reported as primary on a CMS-1500 with multiple lines, only the claim line(s) linked to that inappropriate primary diagnosis may be denied; if an inappropriate principal diagnosis is submitted in Box 67 of a UB-04, the entire claim will be denied.

CMS-1500: denial is applied at the claim-line level for lines associated with the inappropriate primary diagnosis (Box 24E).
UB-04: an inappropriate principal diagnosis in Box 67 results in denial of the entire inpatient claim.

Definitions and Coding Notes

Manifestation codes

DefinitionManifestation codes describe the manifestation of an underlying disease, not the disease itself and therefore cannot be reported as first-listed or principal diagnosis.

Usage implicationWhen a condition is a manifestation, sequence the underlying cause as the principal/first-listed diagnosis per ICD-10-CM guidelines.

Relation to sequencing rulesManifestation codes are handled under the same official coding rules that govern 'code first' and sequela sequencing exceptions.

Code first (sequencing)

RuleWhen a 'Code first' note applies, the underlying condition should be sequenced first if known.

Context'Code first' notes occur with certain codes that are not manifestation codes but may be due to an underlying cause.

ReferenceFollow the ICD-10-CM Official Guidelines for Coding and Reporting for detailed sequencing instructions when 'Code first' notes are present.

MS-DRG 998 (invalid principal diagnosis)

DefinitionMS-DRG 998 represents a discharge reporting a principal diagnosis that is invalid as a principal diagnosis.

ExamplesIncludes diagnoses such as unspecified diabetes mellitus or an unspecified genitourinary tract infection in pregnancy that are insufficient to determine the principal diagnosis for MS-DRG assignment.

Reimbursement impactClaims with a principal diagnosis that maps to MS-DRG 998 indicate the principal diagnosis is not sufficient for DRG assignment and may result in denial or improper payment determination.

Policy Summary

PayerUnitedHealthcare

PolicyUnacceptable Principal and Inappropriate Primary ICD-10-CM Diagnosis Codes for CMS-1500/UB-04 Claims

Policy CodePolicy 2025R5034A

Change TypeRevised code lists

Effective Date

Next Review Date

Key ActionSubmit accurate claims with appropriate procedure and diagnosis codes in accordance with CPT/CMS and ICD-10-CM guidelines.

SourceLink

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