UB-04 (CMS-1450) Form Guide

A UB-04 claim can contain perfect medicine and still fail, because institutional payment is driven less by the diagnosis list than by a handful of administrative fields most clinicians never see. The type of bill, the statement period, the revenue code lines and the discharge status tell the payer what kind of claim this is and which payment methodology applies — get one wrong and the claim suspends, prices incorrectly or denies outright.

What the UB-04 is, and who bills on it

The UB-04, officially the CMS-1450, is the standard institutional claim form maintained by the National Uniform Billing Committee (NUBC). Hospitals bill on it, and so do skilled nursing facilities, hospices, home health agencies, outpatient departments and surgery centres. Its electronic equivalent is the 837I transaction, which carries the same data in segments rather than numbered boxes — the field numbers, called form locators (FL), remain the shared language billers and payers use either way.

The dividing line with the professional claim is the nature of the biller, not the place the patient was seen. Practitioners bill their services on the CMS-1500 (837P) — including services performed inside a hospital — while the facility bills its own charges, room, equipment and ancillary services on the UB-04. Many encounters generate both claims, and mismatches between them are a quiet source of audits and denials. Where the UB-04 sits in the end-to-end claim journey is mapped in our walkthrough of the medical billing process step by step.

The header: whose claim, which patient, what period

The top of the form establishes identity and time — errors here usually reject.

Field	What it holds and why it matters
FL 1 — Provider name, address, phone	The billing facility's information. Must match the enrollment record; a mismatch with the NPI in FL 56 is a classic front-end rejection.
FL 3a / 3b — Patient control / medical record numbers	FL 3a is the facility's patient control number, the key your team uses to trace the claim. FL 3b carries the medical record number linking the claim to the chart.
FL 4 — Type of bill	A four-character code: facility type, bill classification and frequency. It declares whether this is an inpatient, outpatient, interim, corrected or late-charge claim — the wrong type prices the claim under the wrong methodology or denies it as a duplicate.
FL 6 — Statement covers period	The from/through dates of the services on this claim. Must agree with the admission and discharge data and every dated line below; interim bills chain these periods together.
FL 8–9 — Patient name and address	The patient as named on the insurance record. Name and date-of-birth mismatches against the payer's eligibility file are a leading rejection.
FL 10 — Patient date of birth	Used with FL 9 to match the member record; a transposed digit here can reject a clean claim.

The stay: admission and discharge data

The next block tells the payer the shape of the encounter. Admission type (FL 14) records the priority of the admission — emergency, urgent, elective, newborn. Admission source (FL 15) records where the patient came from: physician referral, transfer from another facility, emergency department. Discharge status (FL 17) records where the patient went — home, another hospital, a skilled nursing facility, home health, or expired — and it feeds payment rules: under Medicare's post-acute transfer policy, certain statuses change an inpatient stay from a full DRG payment to a per-diem calculation, so a casually chosen status code can move real money.

Occurrence and value codes: the claim's footnotes

Two code families annotate events and amounts that the charge lines cannot express:

• Occurrence codes and dates (FL 31–34) report dated events relevant to the claim — accident dates, onset dates, transfer and leave-of-absence spans. A missing occurrence code for an accident-related admission invites a coordination-of-benefits investigation; a wrong date can contradict the statement period.
• Value codes and amounts (FL 39–41) report monetary and quantity data the payer needs for pricing and cost sharing — covered and non-covered day amounts, coinsurance and lifetime reserve days, blood quantities, accommodation amounts. These fields look ceremonial until one is wrong and quietly misprices the claim.

The charge lines: revenue codes, HCPCS and totals

FL 42–47 carry the body of the claim. Each line reports a revenue code (FL 42) — a four-digit category describing the service or accommodation: room and board, pharmacy, laboratory, radiology, operating room, emergency department. Where the payer requires it, FL 44 carries the HCPCS or rate code specifying the exact procedure or drug within that category; the pairing of revenue code and HCPCS is where much institutional coding accuracy lives, and where a strong medical coding support process earns its keep, because the two fields validate against each other. FL 46 holds units, FL 47 the line charges. Units that disagree with the statement period — five days of room charges on a three-day statement — are exactly the contradictions scrubbers are built to catch.

The back of the form: payer, provider identifiers and diagnoses

Field	What it holds and why it matters
FL 50 — Payer name	Names the payer for each coverage line (primary, secondary, tertiary), working with the insured fields beside it to route the claim in order.
FL 56 — Billing provider NPI	The facility's National Provider Identifier. Must be the NPI enrolled with that payer for that location.
FL 58–62 — Insured name, relationship, ID, group	Subscriber data for each payer line: policy holder, relationship to the patient, member ID, group number. Errors here break eligibility matching and coordination of benefits.
FL 63 — Treatment authorisation code	The prior authorisation or referral number from the payer. A missing or mismatched number on a service that required approval is a denial no clean-claim statistic can hide.
FL 67 — Principal diagnosis	The condition established after study to be chiefly responsible for the admission. On inpatient claims it anchors the DRG; an inaccurate one is both a payment and a compliance problem.
FL 69 — Admitting diagnosis	The diagnosis recorded at admission, before study. It legitimately differs from FL 67 — confusing the two is a common audit finding.
FL 70 — Patient's reason for visit	Used mainly on outpatient claims: why the patient presented, supporting the diagnoses billed for emergency and clinic encounters.
FL 74 — Principal procedure code and date	The ICD-10-PCS code and date of the principal procedure. Dates outside the statement period are an automatic red flag.
FL 76 — Attending provider	The attending clinician's NPI and name — required for payer matching even on a facility claim.

Common UB-04 errors that cost facilities money

• Wrong type of bill (FL 4) — a final claim billed with an interim frequency, or a correction without the frequency that marks it as one, producing duplicates instead of adjustments.
• Discharge status that misstates the destination (FL 17) — triggers transfer-policy mispricing and audit exposure.
• Revenue code / HCPCS mismatches (FL 42/44) — procedure detail contradicting the revenue category, or a required HCPCS left off.
• Statement period and units that disagree (FL 6/46) — room days or dated lines outside the billed period.
• Missing occurrence or value codes — accident, transfer and cost-sharing data the payer needed, discovered only after the denial.
• Identifier drift — FL 1, FL 56 and FL 76 data no longer matching the payer's enrollment file after a move or re-credentialing.

Most of these are caught before submission when the electronic 837I built from UB-04 data runs through edits that cross-check the locators against each other — which is why clean electronic claim submission matters as much for facilities as for physician practices. The paper form may be retired, but its field logic is permanent: every institutional denial is, underneath, a form locator telling the wrong story.

Frequently asked questions

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