UB-04 Claim Form: Hospital and Facility Billing Reference

The UB-04 is the standardized paper claim form used by hospitals, skilled nursing facilities, inpatient rehabilitation centers, and other institutional providers to bill Medicare, Medicaid, and most commercial payers for facility-based services. Governed by the National Uniform Billing Committee (NUBC) and adopted across payer types through CMS regulations, the UB-04 replaced the UB-92 form in 2007 and remains the foundational document for facility revenue cycle operations. This reference covers the form's structure, field-level mechanics, regulatory drivers, classification rules, and operational tensions that affect claim adjudication outcomes.

• Definition and Scope
• Core Mechanics or Structure
• Causal Relationships or Drivers
• Classification Boundaries
• Tradeoffs and Tensions
• Common Misconceptions
• Checklist or Steps
• Reference Table or Matrix
• References

Definition and Scope

The UB-04 (also designated CMS Form 1450) is the uniform institutional claim form administered by the National Uniform Billing Committee (NUBC) and required by the Centers for Medicare & Medicaid Services (CMS) for institutional billing under Medicare Part A. Its scope extends well beyond Medicare: Medicaid programs in all 50 states, the majority of commercial insurers, TRICARE, and the Federal Employees Health Benefits Program (FEHBP) accept or require the UB-04 for facility claims.

The form's authority derives from the NUBC's role as the recognized standard-setting body under the Health Insurance Portability and Accountability Act of 1996 (HIPAA), which directed the Department of Health and Human Services to adopt uniform electronic and paper transaction standards. The electronic equivalent of the UB-04 is the ANSI ASC X12N 837I (Institutional) transaction set, governed by the Accredited Standards Committee X12 and adopted at 45 CFR Part 162.

Provider types that use the UB-04 include acute care hospitals, critical access hospitals (CAHs), skilled nursing facilities (SNFs), long-term acute care hospitals (LTACHs), inpatient psychiatric facilities, home health agencies, hospice organizations, outpatient hospital departments, federally qualified health centers (FQHCs), and rural health clinics (RHCs). Physician professional services billed under a facility taxpayer identification number may use the CMS-1500 instead — the CMS-1500 Form Guide describes those distinctions in detail.

Core Mechanics or Structure

The UB-04 contains 81 designated data fields called Form Locators (FLs), each with a specific data element, format requirement, and payer-specific population rule. The NUBC Official UB-04 Data Specifications Manual defines permissible codes and reporting requirements for each FL.

Key Form Locator Groups:

• FL 1–11 (Provider Identification): Facility name, address, NPI, and secondary identifiers. FL 56 captures the billing provider NPI, while FL 57–58 may carry legacy provider numbers still required by select Medicaid programs.
• FL 12–16 (Patient Information): Admission and discharge dates, hour of admission, patient status code (FL 17), and type of admission (FL 19). The patient status code is critical — code 30 (still patient) versus code 01 (discharged to home) directly affects interim versus final billing rules.
• FL 31–34 (Occurrence Codes and Dates): Standardized NUBC occurrence codes that communicate events affecting the claim, such as the onset of a condition or coordination-of-benefits triggers. Coordination of benefits workflows depend heavily on accurate occurrence code reporting.
• FL 35–36 (Occurrence Span Codes): Cover date ranges for specific events, such as periods of Medicare Part A benefits exhaustion.
• FL 39–41 (Value Codes and Amounts): Quantify specific dollar or unit amounts associated with a claim — for example, Value Code 50 reports Medicare lifetime reserve days used, which affects cost-sharing liability.
• FL 42–49 (Revenue Codes): The revenue code line items constitute the billing structure core of the UB-04. Each line carries a four-digit NUBC revenue code identifying the service category (e.g., 0270 for medical/surgical supplies, 0450 for emergency room services), units of service, total charges, and a HCPCS/CPT code where required. The HCPCS Level II Codes reference addresses ancillary code requirements that attach to specific revenue code lines.
• FL 67–75 (Diagnosis and Procedure Codes): ICD-10-CM diagnosis codes (up to 25 on FL 67–67Q) and ICD-10-PCS procedure codes for inpatient claims (up to 25 on FL 74–74e). The principal diagnosis on FL 67 is the pivotal driver of Diagnosis-Related Group (DRG) assignment for Medicare inpatient claims.
• FL 76–81 (Attending, Operating, and Other Providers): NPI and name fields for the attending physician, operating physician, and up to two other providers. These fields support medical necessity review and coordination with professional fee claims.

Causal Relationships or Drivers

The UB-04's design reflects regulatory mandates originating from three concurrent federal frameworks. First, the Medicare Conditions of Participation (CoPs) at 42 CFR Part 482 require hospitals to maintain medical records sufficient to support claims, establishing a documentation baseline that the UB-04 must reflect accurately. Second, HIPAA's administrative simplification provisions at 45 CFR Part 162 required convergence on the NUBC data set for all covered entities, driving commercial payer adoption. Third, NUBC releases periodic updates to the UB-04 data specifications — typically annually — that add, retire, or redefine form locator codes in response to new CMS payment policies or legislative changes.

Payer-specific billing guidelines add a fourth driver. Medicare Administrative Contractors (MACs), the regional CMS contractors that process Part A claims, publish Local Coverage Determinations (LCDs) and Billing and Coding Articles that govern specific revenue code and occurrence code combinations. A claim that conforms to the NUBC specification may still reject at the MAC level if it conflicts with an active LCD.

DRG billing relationships illustrate a direct causal chain: the principal ICD-10-CM diagnosis (FL 67), secondary diagnoses flagged as major complicating conditions (MCCs) or complicating conditions (CCs), and the ICD-10-PCS procedure codes collectively determine the MS-DRG weight assigned by the Medicare Severity-Diagnosis Related Groups (MS-DRG) grouper maintained by CMS. A single documentation gap — for example, a coder not capturing a present-on-admission (POA) indicator on FL 67B — can shift DRG assignment and affect reimbursement by thousands of dollars on a single claim.

Classification Boundaries

The UB-04 applies to institutional claims, not professional claims. The operational boundary between the two forms maps to the bill type code entered in FL 4, a three-character NUBC code specifying facility type and bill classification.

Bill Type Code Structure:
- First digit — Facility Type: 1 = Hospital, 2 = SNF, 3 = Home Health, 4 = Religious Non-Medical Health Care Institution, 5 = Intermediate Care Facility, 6 = Clinic/Rehabilitation Facility, 7 = Special Facility (FQHC, RHC, CMHC)
- Second digit — Bill Classification: 1 = Inpatient (Part A), 2 = Inpatient (Part B), 3 = Outpatient, 4 = Other (Part B), 5 = Intermediate Care, 6 = Intermediate Care (Level II), 7 = Subacute Inpatient, 8 = Swing Beds
- Third digit — Frequency Code: 1 = Admit through discharge, 2–3 = Interim (continuing claims), 7 = Replacement, 8 = Void/Cancel

For example, bill type 111 represents an inpatient hospital admit-through-discharge claim. Bill type 131 represents a hospital outpatient claim, which maps to inpatient vs. outpatient billing distinctions governing whether services are paid under the Inpatient Prospective Payment System (IPPS) or the Outpatient Prospective Payment System (OPPS).

The UB-04 does not apply to standalone physician office billing, ambulatory surgery center (ASC) claims submitted on CMS-1500, or durable medical equipment claims when billed by a non-facility supplier. However, hospital outpatient departments billing under the facility's NPI and tax ID do use the UB-04 even when services are functionally similar to physician office services.

Tradeoffs and Tensions

Revenue Code Granularity vs. Processing Overhead

The NUBC revenue code structure contains more than 1,000 defined codes, allowing highly granular service categorization. However, payers frequently accept only a subset of those codes and reject claims with valid NUBC codes that fall outside the payer's adjudication table. Facilities must maintain payer-specific crosswalk tables — adding administrative complexity — or risk denials that require the claim denial management process to resolve.

Charge Description Master (CDM) Accuracy vs. Billing Compliance

Each revenue code line on the UB-04 derives its charge from the facility's Charge Description Master (CDM). CDM entries that have not been updated to reflect current HCPCS codes or revenue code reassignments generate systematic billing errors. The tension arises because CDMs in large hospitals may contain 30,000 or more line items, making continuous maintenance resource-intensive. The medical billing audit compliance framework identifies CDM accuracy as a high-risk area under the OIG Work Plan.

Bundling Rules vs. Accurate Cost Reporting

CMS's Outpatient Prospective Payment System (OPPS) bundles ancillary services — such as certain laboratory and radiology services — into the Ambulatory Payment Classification (APC) payment for the primary procedure. Facilities may list these services on separate revenue code lines reflecting actual charges, yet receive a bundled payment that does not cover each line individually. This creates tension between accurate cost accounting (requiring all charges to appear) and the appearance of overbilling if the billing rationale is not documented. The bundling and unbundling rules reference provides additional context on how CMS enforces these distinctions.

Interim Billing Frequency vs. Claim Accuracy

Long inpatient stays can trigger interim billing (frequency codes 2 and 3 in FL 4) before final discharge information is available. Interim claims carry elevated risk of condition code or occurrence code errors because discharge status and final diagnoses are unknown at the time of submission, requiring subsequent adjustment claims.

Common Misconceptions

Misconception 1: The UB-04 and the 837I are different submission methods for different payers.
Correction: The UB-04 is the paper form; the 837I is its electronic equivalent. Both carry the same data elements defined by the NUBC and ANSI X12. The vast majority of institutional claims are submitted as 837I transactions through a clearinghouse, not as paper UB-04 forms. The form locator numbering from the paper UB-04 maps directly to the 837I loop and segment structure.

Misconception 2: Revenue codes alone determine payment.
Correction: Revenue codes identify service categories and trigger HCPCS code requirements in many cases, but payment under Medicare OPPS is determined by the APC assigned to the HCPCS/CPT code on the revenue code line, not the revenue code itself. Under Medicare IPPS, payment is determined by the MS-DRG grouper operating on diagnosis and procedure codes, making revenue codes informational rather than payment-determinative for inpatient claims.

Misconception 3: The attending physician NPI in FL 76 is optional.
Correction: CMS requires the attending physician NPI for all Medicare inpatient claims and for most Part B outpatient claims involving medical supervision. Omission causes a claim-level rejection under HIPAA 837I validation rules. The National Provider Identifier Standard at 45 CFR § 162.1002 mandates NPI use in covered transactions.

Misconception 4: Condition codes and occurrence codes serve the same function.
Correction: Condition codes (FL 18–28) describe circumstances affecting claim processing — for example, condition code 02 indicates employment-related illness, affecting payer coordination. Occurrence codes (FL 31–34) document specific events on specific dates. The two code sets are structurally distinct and populate different FL ranges; using one in place of the other produces a technically invalid claim.

Checklist or Steps

The following sequence reflects the standard institutional claim preparation workflow for a UB-04/837I submission. This sequence is descriptive of common industry practice, not advisory instruction.

1. Patient account data verification — Confirm patient demographic and insurance information matches the payer's eligibility file. Verify NPI for billing and rendering providers in FL 56 and FL 76–81.
2. Bill type code assignment — Assign the correct three-digit NUBC bill type code to FL 4 based on facility type, service classification, and claim frequency.
3. Admission and discharge data entry — Populate FL 12 (admission date), FL 16 (discharge hour), and FL 17 (patient status code) from the medical record. Confirm patient status code against actual discharge disposition documentation.
4. Condition and occurrence code review — Evaluate payer-specific guidelines and NUBC specifications for required condition codes (FL 18–28) and occurrence codes/dates (FL 31–34). Attach occurrence span codes (FL 35–36) where date ranges apply.
5. Value code population — Identify applicable NUBC value codes for FL 39–41, including covered days, non-covered days, Medicare blood deductible units, and lifetime reserve days.
6. Revenue code line item build — Enter each revenue code line in FL 42–49 with corresponding HCPCS/CPT code, units, and total charges from the CDM. Confirm HCPCS attachment requirements for each revenue code per current NUBC and payer guidelines.
7. Diagnosis and procedure code assignment — Enter ICD-10-CM codes in FL 67–67Q with present-on-admission (POA) indicators for inpatient claims. Enter ICD-10-PCS procedure codes in FL 74–74e. Confirm principal diagnosis selection per ICD-10-CM Official Guidelines for Coding and Reporting (CDC).
8. Total charge reconciliation — Sum all revenue code line charges against the expected total in FL 47. Verify that covered charges align with payer benefit parameters.
9. 837I transaction set generation — Map all UB-04 data elements to the corresponding 837I loops and segments per the ANSI ASC X12 5010 Implementation Guide. Submit via certified clearinghouse.
10. Claim status tracking — Confirm receipt acknowledgment (277CA transaction) from the payer and monitor for claim status (276/277 transaction set) prior to remittance processing through remittance advice ERA workflows.

Reference Table or Matrix

UB-04 Form Locator Summary: Selected Key Fields