5.1 CMS-1500 & UB-04 fields

The two standard claim forms

Medical billing depends on two standardized claim forms, and choosing the correct one is a core CBCS skill. The CMS-1500 is the professional claim used by physicians, non-institutional providers, and suppliers. The UB-04, also called the CMS-1450, is the institutional claim used by hospitals, skilled nursing facilities, home health agencies, and other facilities. The exam expects you to know which form applies to a given provider and what the major fields on each form capture, so learn the forms by their signature fields rather than by memorizing every box.

CMS-1500 (professional claim)

The CMS-1500 is maintained by the National Uniform Claim Committee (NUCC). It is printed in red "drop-out" ink so optical scanners read only the black data the biller enters, never the red guide lines. The form has a carrier block at the top and 33 numbered items. The items you must know:

• Item 1 and 1a — the type of insurance and the insured's ID number.
• Items 2–13 — patient and insured demographics and relationship, plus the authorization signatures: Item 12 (release of information, usually stamped "Signature on File") and Item 13 (assignment of benefits).
• Item 17 and 17b — the referring or ordering provider's name and NPI.
• Item 21 — Diagnosis codes. Enter up to twelve ICD-10-CM codes, labeled A through L. Item 21 also holds the ICD indicator "0" that identifies the codes as ICD-10-CM.
• Item 24 — the six service lines. Each line reports one service: 24A date(s) of service, 24B place of service (POS) code, 24D the CPT/HCPCS procedure code with any modifiers, 24E the diagnosis pointer (letters A–L that tie the service to the matching diagnosis in Item 21), 24F charges, 24G days or units, and 24J the rendering provider's NPI.
• Item 25 — the provider's federal tax ID number (EIN or SSN).
• Item 31 — the signature of the physician or supplier.
• Item 32 — the service facility location.
• Item 33 — the billing provider name, address, and phone, with the billing NPI in 33a.

Because the form has only six service lines, an encounter with more than six services must continue on a second CMS-1500.

A few more CMS-1500 items

Beyond the headline fields, several supporting items appear on the exam. Item 11 records the insured's group or policy number and is where you indicate whether other coverage exists. Item 14 captures the date of the current illness, injury, or pregnancy (last menstrual period), and Item 15 notes another date such as a prior same or similar illness. Item 19 is reserved for additional claim information or narrative notes some payers require. Item 23 holds a prior authorization or referral number when the payer mandates one. When a service needs supporting documentation, the claim references an attachment rather than embedding it. Reading these items correctly helps you catch a claim that will bounce for a missing authorization or an absent onset date.

UB-04 / CMS-1450 (institutional claim)

The UB-04 is maintained by the National Uniform Billing Committee (NUBC) and has 81 field locators (FL). It captures facility data the CMS-1500 does not:

• FL 4 — Type of Bill (TOB): a four-digit code stating the facility type, bill classification, and frequency (whether the claim is original, a replacement, or a void).
• FL 18–28 — Condition codes: circumstances that affect how the claim is processed.
• FL 31–34 — Occurrence codes and dates: significant events such as an accident date.
• FL 39–41 — Value codes: dollar amounts, such as covered days or coinsurance.
• FL 42 — Revenue codes: four-digit codes identifying the department or type of accommodation and service (room and board, pharmacy, laboratory, operating room). Revenue codes are the signature element of institutional billing.
• FL 44 — HCPCS/rate; FL 47 — total charges.
• FL 56 — the billing provider's NPI.
• FL 67 — the principal diagnosis plus other diagnoses; FL 69 — the admitting diagnosis.
• FL 74 — the principal procedure, coded with ICD-10-PCS (inpatient procedures), not CPT.

Institutional inpatient claims report procedures with ICD-10-PCS and are typically reimbursed under DRGs, while the professional CMS-1500 always reports services with CPT/HCPCS codes.

CMS-1500 vs. UB-04 at a glance

Putting it together

When you see a physician office visit, an ambulance transport, or durable medical equipment, reach for the CMS-1500. When you see an inpatient hospital stay, an emergency-department facility charge, or skilled nursing services, reach for the UB-04. The most tested CMS-1500 details are Item 21 (up to twelve diagnoses), Item 24E (diagnosis pointers that connect each service to a diagnosis), and Item 33a (billing NPI). The most tested UB-04 details are the Type of Bill (FL 4) and revenue codes (FL 42). Memorizing these locators lets you spot a misplaced code or a wrong-form error quickly during the exam, and it is exactly the kind of field-identification question the CBCS asks repeatedly.