UB-04 Form (CMS-1450): Institutional Form Locators (FL 1–81), Type of Bill, and Clinical Trial Coding

The UB-04 form—officially designated by the Centers for Medicare & Medicaid Services (CMS) as Form CMS-1450 and maintained by the National Uniform Billing Committee (NUBC)—is the standardized institutional healthcare claim data set in the United States. Consisting of 81 numbered fields called Form Locators (FL 1 through FL 81), the UB-04 and its HIPAA-mandated electronic counterpart, the ASC X12N 837 Institutional (837I) transaction, are used by acute care hospitals, Critical Access Hospitals (CAHs), Skilled Nursing Facilities (SNFs), Outpatient Rehabilitation Facilities, Home Health Agencies (HHAs), and Hospices to bill facility technical fees, room and board, ancillary diagnostics, and institutional clinical trial services.

What Is the UB-04 (CMS-1450) Institutional Claim Form and How Does It Differ from the CMS-1500 (837P) Professional Claim Form?

Under split/provider-based hospital billing rules, a single hospital encounter frequently generates two separate claims: an institutional facility claim on the UB-04 (CMS-1450 / 837I) and a physician professional fee claim on the CMS-1500 form (837P). Understanding the structural boundaries between the two forms prevents duplicate billing and Medicare Administrative Contractor (MAC) edits:

Dimension	UB-04 / Form CMS-1450 (Institutional)	CMS-1500 / Form CMS-1500 (Professional)
Governing Standards Body	National Uniform Billing Committee (NUBC), hosted by the American Hospital Association (AHA)	National Uniform Claim Committee (NUCC), chaired by the American Medical Association (AMA)
HIPAA Electronic Transaction	ASC X12N 837 Institutional (837I) (005010X223A2)	ASC X12N 837 Professional (837P) (005010X222A1)
Eligible Billing Entities	Hospitals (inpatient/outpatient), CAHs, SNFs, Home Health Agencies, Hospices, ESRD facilities, FQHC/RHC facility claims	Physicians (MD/DO), Non-Physician Practitioners (NP, PA, CNS, CRNA, CNM), independent clinical laboratories, DME suppliers (837P)
Field Numbering System	81 Form Locators (FL 1–FL 81)	33 Items / Boxes (Item 1–Item 33)
Primary Line-Item Classifier	4-Digit NUBC Revenue Codes (FL 42) sourced from the hospital chargemaster (paired with CPT/HCPCS in FL 44 for outpatient claims)	CPT / HCPCS Level II Codes (Item 24D) paired with 2-digit Place of Service (POS) codes (Item 24B)
Procedure Coding for Inpatient Stays	ICD-10-PCS (7-character inpatient procedure codes reported in FL 74 / FL 74a–e)	CPT / HCPCS codes for physician inpatient rounds, consultations, and surgical professional fees
Primary Medicare Payment Methodology	IPPS (MS-DRG) for acute inpatient; OPPS (APC) for hospital outpatient; SNF PDPM; HHGM	Medicare Physician Fee Schedule (MPFS) based on Work, Practice Expense, and Malpractice RVUs

What Are the Key UB-04 Form Locators (FL 4 Type of Bill, FL 18–28 Condition Codes, FL 39–41 Value Codes, FL 42 Revenue Codes)?

While the UB-04 contains 81 Form Locators spanning header demographics, situational coding blocks, charge lines, and provider identifiers, hospital revenue cycle analysts and clinical research billing teams focus primarily on seven core structural blocks defined in CMS Medicare Claims Processing Manual Chapter 25:

Form Locator (FL)	Field Name	Format & Coding Rules	Common Institutional Examples
FL 4	Type of Bill (TOB)	4-digit alphanumeric code (0 + Digit 2: Facility Type + Digit 3: Bill Classification + Digit 4: Frequency)	0111 (Hospital Inpatient, Admit-Through-Discharge); 0131 (Hospital Outpatient, Original Claim); 0211 (SNF Inpatient); 0851 (Critical Access Hospital Outpatient)
FL 6	Statement Covers Period	MMDDYY From and Through dates encompassed by the institutional billing cycle	Inpatient admission-to-discharge span or monthly interim billing period
FL 14 / FL 15 / FL 17	Admission Type, Source, & Patient Discharge Status	1-digit Priority/Type of Visit (FL 14), 1-character Point of Origin (FL 15), and 2-digit Discharge Status (FL 17)	FL 17: 01 (Discharged to home/self-care), 02 (Transferred to another short-term general hospital), 03 (Discharged/transferred to SNF), 20 (Expired)
FL 18–28	Condition Codes	Up to 11 two-character alphanumeric NUBC codes indicating special conditions affecting claim processing or payment	Condition Code 30 (Qualified Clinical Trial); 44 (Inpatient admission changed to outpatient prior to discharge); G0 (Distinct medical visits on same day in same revenue center)
FL 31–34 & FL 35–36	Occurrence Codes & Occurrence Span Codes	2-character code + single date (FL 31–34) or From/Through date span (FL 35–36) defining significant clinical or payer events	Occurrence Code 01 (Auto accident date); 11 (Onset of symptoms/illness); Occurrence Span Code 70 (Non-utilization dates); 72 (First/last visit dates)
FL 39–41	Value Codes and Amounts	Up to 12 two-character alphanumeric codes paired with monetary, unit, or numeric identifiers	Value Code 01 (Most common semi-private room rate); 12 (Working aged beneficiary MSP); 80 (Covered days); D4 (8-digit ClinicalTrials.gov NCT number)
FL 42–49	Revenue Code Service Lines (Up to 22 lines per page; up to 450 lines in 837I)	FL 42 (4-digit Revenue Code), FL 43 (Description), FL 44 (HCPCS/Accommodation Rate/HIPPS Code), FL 45 (Service Date), FL 46 (Service Units), FL 47 (Total Charges), FL 48 (Non-Covered Charges)	FL 42 0120 (Room & Board Semi-Private 2-Bed), 0250 (Pharmacy General), 0300 (Laboratory General), 0360 (Operating Room Services), 0450 (Emergency Room), 0636 (Drugs Requiring Detailed Coding)
FL 66–75	ICD-10-CM Diagnoses, POA Indicators, & ICD-10-PCS Procedures	FL 67 (Principal Diagnosis + Present on Admission [POA] indicator for inpatient), FL 67A–Q (up to 17 Other Diagnoses), FL 69 (Admitting Diagnosis), FL 74/74a–e (Principal & Other ICD-10-PCS Inpatient Procedures)	POA indicators: Y (Present at admission), N (Not present at admission), U (Documentation insufficient), W (Clinically undetermined)
FL 56 & FL 76–79	Billing Facility NPI & Attending/Operating Physician NPIs	10-digit National Provider Identifier (NPI) of the billing institution (FL 56) and the Attending Physician (FL 76) and Operating Physician (FL 77)	Attending Physician NPI and full name are mandatory on all inpatient and outpatient institutional claims

Deconstructing the 4-Digit Type of Bill (TOB) in Form Locator 4

Every UB-04 claim is routed through payer adjudication engines by the 4-digit Type of Bill (TOB) in FL 4 (where the leading 0 is omitted in the 3-digit 837I CLM05-1/CLM05-3 representation):

• Digit 1 (Leading Zero): Always 0 on paper UB-04 forms.
• Digit 2 (Type of Facility): Identifies the institutional category—1 (Hospital), 2 (Skilled Nursing Facility), 3 (Home Health), 7 (Clinic, including RHC `071X`, Hospital-Based Renal Dialysis `072X`, and FQHC `077X`), or 8 (Special Facility, including Hospice `081X`/`082X` and Critical Access Hospital `085X`).
• Digit 3 (Bill Classification): Specifies the setting within that facility—for hospitals (`01XX`), 1 = Inpatient (Including Medicare Part A), 2 = Inpatient (Medicare Part B Only, when Part A benefits are exhausted or no Part A stay qualifies), 3 = Outpatient (`013X`), and 4 = Other (for non-patient laboratory specimen referrals, `014X`).
• Digit 4 (Frequency Code): Tells the payer how this claim relates to the episode of care:
  • 1 = Admit Through Discharge Claim (single consolidated bill for the entire episode).
  • 2 = Interim — First Claim (used for long inpatient, SNF, or home health stays).
  • 3 = Interim — Continuing Claim.
  • 4 = Interim — Last Claim (includes discharge date and discharge status).
  • 7 = Replacement of Prior Claim (Adjustment) (replaces a previously adjudicated claim in full).
  • 8 = Void / Cancel of Prior Claim (cancels a previously submitted claim).

How Are Condition Code 30, Value Code D4 (8-Digit NCT Number), and Modifiers Q0/Q1 Reported on Institutional Clinical Trial Claims (837I)?

When an academic medical center or community hospital bills Medicare for routine care items and services furnished to a beneficiary enrolled in a Qualifying Clinical Trial under Medicare National Coverage Determination (NCD) 310.1, institutional clinical trial claim coding on the UB-04 (and 837I) differs structurally from professional CMS-1500 billing:

1. Condition Code 30 in FL 18–28 (Inpatient & Outpatient): Enter Condition Code 30 (Non-Research Services Provided to All Patients Enrolled in a Qualified Clinical Trial) in one of the Condition Code fields (FL 18–28; 837I Loop 2300 HI segment with qualifier BG). Condition Code 30 is the institutional equivalent of the professional claim line modifier Q1 for inpatient stays where line-level HCPCS modifiers do not apply.
2. Value Code D4 + 8-Digit NCT Number in FL 39–41 (Inpatient & Outpatient): Enter Value Code D4 in FL 39–41 paired with the 8-digit numeric ClinicalTrials.gov National Clinical Trial (NCT) identifier (stripping the alpha prefix NCT; for example, NCT01234567 is entered as 01234567.00 on paper or in the 837I Loop 2300 Value Information HI segment with qualifier BE). If the trial is not registered on ClinicalTrials.gov or is non-interventional, CMS accepts 99999999 when permitted by MAC guidance.
3. Secondary Diagnosis ICD-10-CM Z00.6 in FL 67A–67Q (Inpatient & Outpatient): Report ICD-10-CM code Z00.6 (Encounter for examination for normal comparison and control in clinical research program) as a secondary diagnosis in FL 67A–67Q (837I Loop 2300 HI segment with qualifier ABF). On inpatient MS-DRG claims, placing Z00.6 in the principal diagnosis position (FL 67) is an error that distorts DRG grouping.
4. HCPCS Modifiers Q0 and Q1 in FL 44 (Outpatient TOB 013X / 085X Only): Because hospital outpatient claims (billed under OPPS APCs) carry line-item HCPCS codes in FL 44 alongside Revenue Codes in FL 42, outpatient clinical trial claims must append Modifier Q1 (routine clinical service provided in a clinical research study) or Modifier Q0 (investigational clinical service provided in a clinical research study) directly to the applicable HCPCS line items in FL 44. For investigational devices billed under an FDA-approved Investigational Device Exemption (IDE) study, the hospital also reports Revenue Code 0624 in FL 42 and the FDA IDE number using Value Code FD or the corresponding 837I Loop 2300 REF*LX segment.
5. Splitting Covered Routine Costs from Sponsor-Paid Items (FL 47 vs. FL 48): Items provided free of charge by the trial sponsor or paid by the research grant must either be carved out to the research sponsor sub-account via the hospital chargemaster split-billing scrub before claim generation or reported as non-covered charges in FL 48 (with appropriate no-pay coding when required for Medicare Secondary Payer or device credit tracking) so Medicare is never billed for sponsor-funded procedures.