Every billing department has dealt with rejected Medicare claims because someone mixed up a form locator or entered the wrong diagnosis code. The UB 04 claim form determines whether your facility gets paid this month or spends weeks resubmitting corrections.
We put together this field-by-field breakdown because billing manuals tend to overcomplicate things. If you need to train someone new or just want a reference that doesn’t require a decoder ring, this guide covers what actually goes in each box and why payers care about it.
The CMS-1450 form is what hospitals and institutional facilities use to bill insurance. The National Uniform Billing Committee (NUBC) designed it specifically for facility services, it’s completely different from the CMS 1500 that doctors’ offices use for professional claims.
You’ll use this form for inpatient and outpatient billing, entering everything from revenue code details to diagnosis code information. Most places handle Medicare and Medicaid submissions through electronic claim submission now, but the data requirements haven’t changed. Every field still needs to be accurate, or you’re looking at denials.
You’ll pull out this form when you’re billing for:
Now, let’s get into the details of each field.
The UB 04 claim form is divided into what we call “form locators” or “FLs” for short. Each one is numbered, and each has specific information it needs. Some are mandatory, some are situational, and some you’ll rarely touch. Here’s what goes where.
This is where you put your facility’s information. Seems simple, right? But here’s the thing, it needs to match exactly what you’ve registered with the insurance company. We’ve seen claims denied because someone abbreviated “Street” as “St.” when the payer had “Street” spelled out in their system.
List your legal facility name first, then your complete mailing address, and finally your main phone number. Don’t use shortcuts here. If your facility is “Memorial Hospital of Greater Springfield,” don’t write “Memorial Hosp.” The insurance company’s computer is looking for an exact match.
Most of the time, you’ll leave this blank. But if you’ve got a centralized billing office or you use a third-party billing company, this is where payment should actually go. If payments come directly to the facility address in FL 1, skip this field entirely.
This is your internal claim tracking number. Pick a system that works for you and stick with it. When the insurance company calls with questions (and they will), this number helps you find the right claim in about 10 seconds instead of 10 minutes.
This is the patient’s medical record number from your system. These two numbers together (3a and 3b) create a foolproof way to connect the claim to the right patient encounter in your records. Don’t mix them up, one tracks the claim, the other tracks the patient.
Here’s where things get technical, but stay with me. This four-digit code tells the payer what kind of facility you are and what kind of bill you’re sending. It’s like a secret code, except everyone in healthcare billing knows what it means.
For example, 0131 means hospital inpatient, admitted through discharge claim.
Your facility’s nine-digit federal tax ID goes here. This needs to match what Medicare and other payers have on file. One transposed number and you’re looking at a rejection.
These are the “from” and “to” dates for the services on this bill. For inpatient stays, it’s admission to discharge. For outpatient claims, it’s the date range of services you’re billing on this particular claim.
Use the MMDDYY format. So June 15, 2024, would be 061524. The dates need to match up with your revenue code dates later in the claim, or you’ll have explaining to do.
This seems obvious, but hear me out. The name has to match the insurance card exactly. Not what’s in your EMR, not what the patient told you at registration, but what’s on the insurance card.
Last name first, then first name, then middle initial. If Mary Elizabeth Johnson goes by “Beth,” but her insurance card says “Mary,” you write Mary. We’ve seen claims denied because someone used “Bob” instead of “Robert.”
Complete mailing address. No P.O. boxes unless that’s genuinely the patient’s address. The insurance company uses this to verify the patient is who they say they are, so accuracy matters.
MMDDYYYY format. So January 5, 1985, becomes 01051985. Insurance companies use birthdate as a key identifier, so one wrong digit can send your claim into the rejection pile.
M for male, F for female, U for unknown. Match what the insurance company has on file. If there’s a mismatch, you’re headed for a denial.
Enter the admission date in MMDDYYYY format. For inpatient claims, this establishes when the episode of care began. It’s also important for meeting various reporting requirements.
The hour of admission using military time (00-23). So if someone was admitted at 2:30 PM, you’d put 14. This helps establish the exact start of the inpatient stay.
This tells the story of how urgent the admission was. Code 1 means emergency, the patient needed immediate attention. Code 2 is urgent but not quite emergency level. Code 3 is elective, meaning the admission was planned. Code 4 is for newborns, code 5 for trauma center admissions, and 9 for information not available.
Why does this matter? Because it helps justify the level of care provided. An elective surgery has different documentation requirements than an emergency trauma case.
Where was the patient before they came to you? Code 1 means they came from a physician’s office. Code 7 is the emergency room. Code 4 means they transferred from another hospital. Code 5 indicates transfer from a skilled nursing facility. Code 8 is court or law enforcement.
This information helps insurance companies understand the patient’s care journey and whether the admission was appropriate.
Military time again, showing what hour the patient left. For inpatient claims, this helps calculate the exact length of stay. Sometimes that extra hour matters for billing purposes.
This two-digit code explains where the patient went after leaving your facility. Code 01 means home (the outcome everyone hopes for). Code 03 is discharge to a skilled nursing facility. Code 20 means the patient died. Code 30 indicates they’re still a patient. Code 07 is noteworthy, that’s “left against medical advice.”
These codes aren’t just administrative; they’re used for quality reporting and outcomes tracking.
You’ve got space for up to eleven two-digit condition codes here. These provide extra context about the claim that doesn’t fit anywhere else. For instance, condition code 02 tells the payer this was a work-related injury.
Code 20 means the patient specifically asked for the billing. Code 21 indicates you’re billing to generate a denial notice that the patient needs. Code 07 indicates treatment of a non-terminal condition for hospice patients.
Don’t throw random code in here. Only use ones that actually apply to this specific claim. Each payer may have particular codes they want to see for certain situations.
If the patient’s condition resulted from an accident, enter the two-letter state abbreviation where the accident occurred. This is particularly important for auto accidents and workers’ compensation claims.
This field is typically left blank or used for specific payer requirements. Check with your payers to see if they need anything here.
These four sets of fields (31a/31b, 32a/32b, 33a/33b, 34a/34b) let you report significant events related to the claim. The “a” field gets a two-digit occurrence code, and the “b” field gets the date in MMDDYY format.
Common occurrence codes include:
These codes and dates help establish timelines and liability, which can be crucial for payment.
These work like occurrence codes but for events that span a period of time rather than happening on a single day. You’ll enter a two-digit code and then “from” and “through” dates. For example, you might use occurrence span code 70 to indicate qualifying stay dates for Medicare patients, or code 71 for prior stay dates.
If someone other than the patient is financially responsible for the bill, their information goes here. This could be a parent for a minor, a legal guardian, or someone else who’s agreed to pay. Include their full name and complete address.
These three sets of fields (39a/39b/39c/39d, 40a/40b/40c/40d, 41a/41b/41c/41d) are for reporting various monetary values that apply to the claim. Each “a” position gets a two-digit value code, and each “b” gets the corresponding dollar amount.
Common value codes include:
These codes provide the financial context that payers need to calculate correct payment amounts.
Revenue codes are four-digit codes that categorize the types of services you provide. Each line on the claim gets its own revenue code.
You need to group similar services under the same revenue code. Don’t split up room charges across multiple lines unless there’s a good reason. The last line should always be revenue code 0001, which is the total charges line. The more organized your revenue codes, the easier the claim is to read and process.
Most billing systems automatically populate this based on the revenue code. It’s a text description of what the revenue code represents. Make sure it matches, don’t have code 0450 with a description of “Pharmacy.” Consistency matters.
While revenue codes categorize services broadly, HCPCS and CPT codes get specific. These procedure codes describe exactly what was done. Use modifiers when appropriate to add detail about how the procedure was performed.
The HCPCS code should make sense with the revenue code on the same line. If your revenue code is 0250 (pharmacy), your HCPCS code better be for a drug, not a lab test. For skilled nursing and home health, you might use HIPPS codes here instead.
This is the specific date the service on this line was provided, in MMDDYY format. For charges that span multiple days (like room charges), use the first date of service. These dates need to fall within the statement’s covers period from FL 6. If they don’t, you’ve got a problem.
This is how many units of service you provided. For room charges, it’s the number of days. For a procedure, it’s how many times you performed it. For drugs, it might be based on dosage. For anesthesia, it could be time units. The unit of measure depends on the type of service.
Multiply your units by your charge per unit, and this is what you get. Enter the amount without dollar signs or commas, but do include cents. So $1,500.00 becomes 150000. Your total charges from all lines should add up to match the total on the 0001 revenue code line.
If you know certain charges on this line aren’t covered by the patient’s insurance, separate them out here. This helps set expectations and can speed up processing by making it clear what you expect the payer to pay versus what you’ll bill the patient.
This field is typically reserved for future use or specific payer instructions. Most of the time, you’ll leave it blank.
Write out the insurance company’s name. Line A is for the primary payer, line B for secondary, line C for tertiary. The name needs to match what the payer calls themselves. Is it “Blue Cross Blue Shield” or “BCBS“? Check the payer’s guidelines. Getting the payer name exactly right helps ensure the claim routes to the correct payer for processing.
This is your provider identifier with that specific payer. It could be your NPI, a legacy provider number, or a plan-specific ID. Different payers want different things here, so you need to know each payer’s preferences. Lines A, B, and C correspond to the payers listed in FL 50.
This indicates whether you have the patient’s authorization to release medical information to the payer. Use “Y” for yes or “I” for informed consent on file. If you don’t have authorization, you’ll have problems getting paid because the payer can’t review the medical necessity of services.
This shows whether the patient has assigned their benefits to be paid directly to your facility. “Y” means yes, the patient wants payment to go to you. “N” means payment goes to the patient. You want this to be “Y” in almost all cases.
If the payer has already made payments toward this claim, enter those amounts here. This is common when dealing with payment corrections or secondary payers. It helps establish what’s already been paid, so the payer knows what they still owe.
This is your estimate of what the payer owes after any prior payments or adjustments. Most payers ignore this field and calculate their own amount due, but some require it. It’s basically your best guess at what you’ll get paid.
Your facility’s 10-digit NPI goes here. This is separate from any legacy numbers you might use. Every claim needs a valid, active NPI, or it won’t process. Double-check this number because transpositions happen more often than you’d think.
If a payer requires a different identifier beyond your NPI, it goes here. This could be your Medicare PTAN, Medicaid provider number, or commercial payer-specific ID. Lines A, B, and C correspond to the payers in FL 50.
The person who owns the insurance policy might not be the patient. If you’re billing for a child, the insured is probably a parent. If you’re billing for a spouse, it’s probably the other spouse. Use the exact name from the insurance card, in last name, first name, and middle initial format. Lines A, B, and C match up with the payers in FL 50.
This code indicates the patient’s relationship to the insured party. Code 01 means spouse, 18 means self (patient is the policyholder), 19 means child, 20 means employee, 39 means organ donor, and 40 means cadaver donor. Getting this right helps payers determine coverage eligibility.
This is the insurance policy number, certificate number, or member ID straight from the card. Copy it exactly, every letter, every number, every dash, every space (or lack of space). This is how the payer’s system identifies the patient. Get it wrong, and the claim won’t process. Lines A, B, and C correspond to your payers in FL 50.
If the insurance is through a group plan (like through an employer), the group name goes here. Sometimes payers use this to verify eligibility and determine plan benefits. Check the insurance card carefully.
This is the group number or group plan code from the insurance card. Like the member ID, copy it exactly as shown. Group numbers help identify which benefit plan applies to this patient.
If you obtained pre-authorization or a referral authorization from the payer before providing services, the authorization number goes here. This is critical for certain procedures and specialties. No auth number when one was required? That’s an automatic denial.
For secondary or tertiary claims, enter the document control number (or claim number) assigned by the primary payer. This helps the coordination of benefits by linking the claims together. The secondary payer uses this to request information from the primary payer.
If the patient’s insurance is employment-related, enter the employer’s name here. This is particularly important for workers’ comp claims and for verifying group coverage eligibility.
This tells the payer what coding system you’re using for diagnoses and procedures. For diagnosis codes, you’ll use “0” for ICD-10-CM (which is the current standard in the U.S.). This field ensures the payer interprets your codes correctly.
This is arguably one of the most important fields on the entire form. The principal diagnosis is the main reason for this hospitalization or encounter, determined after study. Not the admitting diagnosis, not every problem the patient has, but the primary condition that, after evaluation, was chiefly responsible for this admission.
You’ll use ICD-10-CM codes here. Include the decimal point. Make sure you’re using the most specific code available. A vague diagnosis code is a fast track to a denial or a request for medical records.
Here’s where you list secondary diagnoses, conditions that existed at admission or developed during the stay, and affected treatment. You have room for up to 17 additional diagnosis codes (67A through 67Q). List them in order of clinical significance.
These secondary diagnoses do more than fill up space. They tell the complete story of the patient’s clinical picture and help justify the resources used. They can also affect your facility’s case mix and payment rates under various reimbursement methodologies.
This is the diagnosis code that was documented at the time of admission, basically, why you admitted the patient in the first place. It might differ from the principal diagnosis in FL 67 if the patient’s condition evolved or if further testing revealed a different primary problem.
For outpatient claims, especially emergency room visits, these fields capture the patient’s chief complaint or reason for the visit. Use ICD-10-CM diagnosis codes here as well. You can report up to three reason codes.
This field is used primarily for SNF claims. It’s where you’d report the HIPPS code under the SNF PPS system. Most hospitals won’t use this field, but if you work in a skilled nursing facility, you’ll need to get this right for proper payment.
If the patient’s condition was caused by an external event, like a fall, car accident, assault, or other injury, report the external cause of injury code here. These are ICD-10-CM codes from the V, W, X, or Y chapters. You can report up to three ECI codes.
These codes are important for public health tracking and can also affect liability determination, especially in auto accident or workers’ comp cases.
For inpatient claims, this is where you report the principal surgical or diagnostic procedure and the date it was performed. Use ICD-10-PCS codes (not CPT codes) and format the date as MMDDYY. The principal procedure is the one most significant to the treatment of the principal diagnosis.
You can report up to five additional procedures here (74a through 74e). Each gets its own ICD-10-PCS code and date. List them in order of significance to the patient’s care.
These procedure codes help justify the level of resources used and can affect DRG assignment and payment for inpatient claims.
The attending physician is the doctor who was primarily responsible for the patient’s care. This is a multi-part field. You’ll enter:
The NPI needs to be active and valid. Claims get denied for incorrect or inactive NPIs all the time. Double-check this number.
If there were a surgery, the operating surgeon would go here. Same format as FL 76, name, NPI, and qualifier. If there was no surgery, leave it blank. This provider must match the principal procedure in FL 74.
These two fields let you report additional providers who played significant roles in the patient’s care. This might include:
Always include the provider’s name, NPI, and appropriate qualifier code. These fields help track referral patterns and ensure proper credit for care coordination.
This is your catch-all field for anything that doesn’t fit anywhere else on the claim. You might use it to explain unusual circumstances, provide additional context, or clarify something that might otherwise confuse the payer.
Keep remarks brief and relevant. Don’t write a novel here, but do include information that could prevent a denial or speed up processing. Some examples: “Patient transferred mid-stay,” “Services delayed due to patient request,” or “Auth number pending at time of service.”
This field has multiple purposes depending on payer requirements. Some payers use it for taxonomy codes, some for condition codes that didn’t fit in FL 18-28, and some for other payer-specific information. Check your payer guidelines to see if they require anything here.
Each position (A through D) can hold different information, and you’ll often need to include a qualifier to indicate what type of code you’re reporting.
Getting the UB-04 right isn’t just about filling in boxes, it’s about understanding the story your claim tells. Every field connects to others. Your diagnoses need to support your procedures. Your procedures need to match your revenue codes. Your dates need to be consistent throughout.
Here are some hard-won lessons from years of helping providers with claims:
Check insurance eligibility before providing services. Confirm you have current demographic information. Make sure you understand the patient’s benefits and any authorization requirements. An ounce of prevention at registration saves hours of claim correction later.
Use the same formats every time. Train your staff on proper entry techniques. Create templates for common claim types. When everyone does things the same way, errors drop dramatically.
Different insurance companies have different quirks. Some want specific condition codes. Some require certain remarks. Some have unique identifier requirements. Keep a reference guide for each of your major payers.
Don’t just trust your billing system. Have someone actually look at claims before they go out. Check that diagnosis codes make sense. Verify that charge amounts are reasonable. Confirm that provider NPIs are correct.
Every denial is a learning opportunity. Don’t just correct it and resubmit, figure out why it happened and how to prevent it next time. Keep a log of common denial reasons and share solutions with your team.
Payers can request medical records for any claim. Make sure your documentation supports what you’re billing. The clinical record should clearly show medical necessity for services, support your principal diagnosis, and document all procedures claimed.
The reality is that one wrong revenue code or a mismatched diagnosis code creates more work for everyone. Medicare claims get rejected, payments get delayed, and someone has to figure out what went wrong. Understanding the UB 04 claim form means fewer of those headaches.
Most billing software handles electronic claim submission, but the system only works if the data going in is correct. Whether you’re processing Medicare and Medicaid or commercial insurance, the CMS-1450 form hasn’t gotten any more forgiving. Know what belongs in each form locator for both inpatient and outpatient claims, and your acceptance rates will show it.
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