The CMS-1500 Form: The Gold Standard of Medical Claims

In the world of medical billing, the CMS-1500 (Health Insurance Claim Form) is the standard paper claim form used by non-institutional healthcare providers to bill Medicare and most other health insurance payers. While electronic billing (EDI 837P) has largely superseded paper claims, the layout and data requirements of the CMS-1500 remain the blueprint for how professional services are reported.

What is the CMS-1500?

The CMS-1500 is a red-ink-on-white-paper form maintained by the National Uniform Claim Committee (NUCC). It is designed to be read by Optical Character Recognition (OCR) scanners.

• Who uses it? Medical Labs, Physicians, non-physician practitioners (NPs, PAs), clinical social workers, ambulance services, and durable medical equipment (DME) suppliers.
• Who is it NOT for? Hospitals and institutions (they use the UB-04 form).

The Purpose of the Form

The form serves a single critical purpose: Reimbursement. It tells the insurance payer:

1. Who received care (The Patient).
2. Who provided the care (The Provider).
3. Why the care was needed (Diagnosis Codes).
4. What services were performed (Procedure Codes).

Field-by-Field Guide to the CMS-1500

The form is divided into three main sections: The Header (Payer info), Patient/Insured Information (Boxes 1-13), and Physician/Supplier Information (Boxes 14-33).

Section 1: Carrier Block

• Top Right Header: This blank space is where the name and address of the insurance payer (e.g., Cigna, Medicare, Blue Cross) are entered.

Section 2: Patient and Insured Information (Boxes 1–13)

This section establishes who the patient is and who holds the insurance policy.

• Box 1 (Medicare/Medicaid/Tricare/etc.): Check the box indicating the type of health insurance coverage applicable to the claim.
• Box 1a (Insured’s ID Number): The identification number found on the patient's insurance card. Crucial for matching the patient to the policy.
• Box 2 (Patient’s Name): Last name, First name, Middle initial. Must match the insurance card exactly.
• Box 3 (Patient’s Birth Date & Sex): MM/DD/YYYY format. Check the appropriate box for sex.
• Box 4 (Insured’s Name): If the patient is the policyholder, list their name. If the patient is a dependent (e.g., a child), list the parent’s name here.
• Box 5 (Patient’s Address): The physical address of the patient.
• Box 6 (Patient Relationship to Insured): Check "Self" if the patient is the policyholder. Otherwise, check Spouse, Child, or Other.
• Box 7 (Insured’s Address): If the insured is different from the patient, enter their address here. If same, leave blank or enter "Same."
• Box 8 (Reserved for NUCC Use): Leave blank.
• Box 9 (Other Insured’s Name): Used only if there is secondary insurance. If filled, boxes 9a-9d must also be completed.
• Box 10 (Is Patient’s Condition Related To):
  • 10a (Employment): Check YES if this is a Workers' Comp case.
  • 10b (Auto Accident): Check YES if due to a car crash (indicates Auto Insurance is primary).
  • 10c (Other Accident): Check YES for slip-and-fall or other liability cases.
• Box 11 (Insured’s Policy Group or FECA Number): The Group Number on the insurance card.
  • 11a (Insured's Date of Birth): DOB of the primary policyholder.
  • 11b (Other Claim ID): Usually left blank or used for property/casualty claim numbers.
  • 11c (Insurance Plan Name): Name of the insurance plan.
  • 11d (Is there another health benefit plan?): If YES, complete Box 9.
• Box 12 (Patient’s or Authorized Person’s Signature): "Signature on File" (SOF) is usually accepted here. This authorizes the release of medical information to process the claim.
• Box 13 (Insured’s or Authorized Person’s Signature): "Signature on File" (SOF). This authorizes payment of benefits directly to the provider (Assignment of Benefits).

Section 3: Physician or Supplier Information (Boxes 14–33)

This section details the medical necessity and services rendered.

• Box 14 (Date of Current Illness/Injury/Pregnancy): The date the symptoms began or the date of the accident.
• Box 15 (Other Date): Used for specific instances like "Refill Date" or "Initial Treatment Date."
• Box 16 (Dates Patient Unable to Work): Required for Workers' Comp claims to indicate disability periods.
• Box 17 (Name of Referring Provider): If a specialist is billing, the referring doctor's name goes here.
  • 17a: Referring provider's state license number (rarely used now).
  • 17b: NPI (National Provider Identifier) of the referring doctor. Critical field.
• Box 18 (Hospitalization Dates): Only used if the services were rendered during an inpatient stay.
• Box 19 (Additional Claim Information): A narrative field for comments or specific qualifiers (e.g., "Homebound" for home health).
• Box 20 (Outside Lab?): Check YES if the doctor paid an outside lab to run tests and is passing the cost to the insurance. Enter the purchase price.
• Box 21 (Diagnosis or Nature of Illness or Injury):
  • Enter the ICD-10-CM codes here (A-L).
  • Example: A: J01.90 (Acute sinusitis).
  • These codes justify the procedures listed in Box 24.
• Box 22 (Resubmission Code): Used when correcting a previously denied claim. (Code 7 = Replacement of prior claim).
• Box 23 (Prior Authorization Number): If the service required pre-approval, the authorization number goes here.
• Box 24 (The Service Lines): The heart of the bill. There are 6 lines available.
  • 24A (Date(s) of Service): From and To dates.
  • 24B (Place of Service): A 2-digit code (e.g., 11 = Office, 21 = Inpatient Hospital, 23 = ER).
  • 24C (EMG): Emergency indicator (Y/N).
  • 24D (Procedures, Services, or Supplies): Enter the CPT or HCPCS code and any necessary Modifiers (e.g., 99213 - 25).
  • 24E (Diagnosis Pointer): Links the procedure to the diagnosis in Box 21. (e.g., enter "A" to link to the first diagnosis).
  • 24F (Charges): The dollar amount billed for the service.
  • 24G (Days or Units): How many times the service was performed (usually "1").
  • 24H (EPSDT Family Plan): Used for Medicaid Early and Periodic Screening.
  • 24I (ID Qualifier): Identifies the type of ID in 24J.
  • 24J (Rendering Provider ID): The NPI of the specific doctor who saw the patient (if different from the group NPI in Box 33).
• Box 25 (Federal Tax ID Number): The provider’s EIN or SSN.
• Box 26 (Patient’s Account No.): The provider’s internal account number for the patient (helps with posting payments later).
• Box 27 (Accept Assignment?): Check YES. This means the provider agrees to accept the insurance's allowed amount as payment in full (minus co-pays/deductibles).
• Box 28 (Total Charge): The sum of all lines in 24F.
• Box 29 (Amount Paid): Any amount the patient paid at the time of the visit (e.g., co-pay).
• Box 30 (Reserved for NUCC Use): Usually left blank.
• Box 31 (Signature of Physician or Supplier): The provider signs here (electronic signatures are accepted) with the date.
• Box 32 (Service Facility Location Information): The name and address where the services were actually performed (e.g., the specific clinic address).
  • 32a: NPI of the facility.
• Box 33 (Billing Provider Info & Ph #): The name, address, and phone number of the practice or group getting paid.
  • 33a: The Group NPI number.

Common Errors to Avoid

• Missing NPIs: Ensure referring and billing NPIs are correct.
• Diagnosis Pointers: Failing to link the procedure (Box 24E) to the correct diagnosis (Box 21) causes "Medical Necessity" denials.
• Name Mismatches: The name in Box 2 must match the insurance card exactly (e.g., "Robert" vs. "Bob").