Which UB-04 form locators cause claim rejections?
No official list ranks UB-04 locators by rejections, but the locators to check first are the ones CMS makes required, format-specific or dependent on another field: type of bill, statement period, discharge status, revenue and HCPCS lines, service dates, billing NPI, authorization and diagnosis.
Written by Salman Saeed, CEO and Co-Founder · Reviewed by a Certified Medical Coder · 
In short: check FL 4, 6, 17, 42, 44, 45, 56, 63 and 67 before release. These are the locators where Chapter 25 sets a hard requirement or format, and fixing every flagged field in one pass avoids a second return.
Which UB-04 form locators cause claim rejections?
No official list ranks UB-04 locators by rejection volume, and CMS does not publish one. This post orders the locators by where the Medicare Claims Processing Manual makes the entry required, fixes its format or ties it to another field, since those are the fields a front-end edit can check. Your own clearinghouse report will show which ones hit your claims most.
A rejection is a front-end return that stops the claim before it is adjudicated, while a denial is a payer decision on a claim it accepted. Our glossary explains rejection vs denial. The edits your clearinghouse and payer apply sit on top of Medicare's, so confirm each one in their manuals.
Which header and patient locators need checking first?
The header locators are small, required and format-specific. Chapter 25, section 75, sets the format for each.
| Locator | What Chapter 25 requires | What to check before release |
|---|---|---|
| FL 4 type of bill | Required, four digits; CMS ignores the leading zero | Four characters, and the facility type and frequency match the claim you are sending |
| FL 5 federal tax number | Required, format NN-NNNNNNN | Entered as two digits, a hyphen and seven digits |
| FL 6 statement period | Required, beginning and ending dates in MMDDYY | From and Through dates match the first and last service dates on the lines |
| FL 8 to 10 patient name, address, birth date | Required; if the birth date is unknown, zeros in all eight digits | Name and birth date match the payer's eligibility response |
| FL 11 patient sex | Required, M or F | Only M or F is entered |
| FL 14 and 15 priority and point of origin | Required; FL 15 is not required on bill type 014X | Both populated from registration, with FL 15 skipped only on 014X |
| FL 17 discharge status | Required for Part A inpatient, SNF, hospice, home health and outpatient hospital | Populated on outpatient hospital claims too, not just inpatient |
A bad type of bill can come back with remark code MA30, which X12 defines as a missing, incomplete or invalid type of bill. The detail on the digits is in type of bill codes explained.
Which service-line locators need the closest check?
Service-line fields are where facility claims differ most from professional claims. The rules come from Chapter 25 sections 75.4 and 75.5.
| Locator | What Chapter 25 requires | What to check before release |
|---|---|---|
| FL 42 revenue code | One revenue code beside each charge in FL 47; ascending order; not repeated on a bill where possible; 0001 as the total line | Every charge has a code, codes run in ascending order, and the 0001 line equals the sum of the charges |
| FL 44 HCPCS or rate | HCPCS for outpatient services; accommodation rate on inpatient bills | Every outpatient revenue code line that needs a service code carries its HCPCS code |
| FL 45 service date | Required on outpatient bills, one date per iteration of every revenue code | One dated line per service date, not one line with a range |
| FL 46 units | Units equal the number of times a HCPCS service was performed | Units match the number of times each HCPCS service was performed |
| FL 47 and 48 charges | Total charges per revenue code; non-covered charges per revenue code | Line totals add up to the 0001 line, with non-covered charges kept separate |
| FL 56 billing NPI | Required | NPI is the billing provider's own enrolled NPI |
The line-date rule in FL 45 catches teams that roll visits up. Chapter 25 gives the example directly: if a service is rendered five times during the billing period, the revenue code and HCPCS code must be entered five times, once for each service date. Our guide to choosing the right revenue code covers how FL 42 and FL 44 pair.
What do payer, diagnosis and provider locators add?
These locators matter when a claim looks complete but conflicts with the payer's record or with another field.
| Locator | What Chapter 25 requires | What to check before release |
|---|---|---|
| FL 50 payer | If Medicare is primary, enter Medicare on line A | Primary payer on line A, Medicare on line B or C when it is secondary |
| FL 60 insured's unique ID | Required on line A | ID copied exactly from the card or eligibility response |
| FL 63 authorization code | Situational, required when the payer assigned an authorization or referral number and the services were preauthorized | Number from scheduling carried onto the claim |
| FL 67 principal diagnosis | Full ICD-10-CM code, seven digits where applicable, decimal implied, no zero filling | Complete code, no zero padding, no decimal typed in |
| FL 70 reason for visit | Required on 013x and 085x when FL 14 is 1, 2 or 5 and revenue code 045x, 0516 or 0762 is reported | ED and observation claims on 013x carry a reason for visit when those conditions are met |
| FL 76 attending provider | Required when the claim has any service other than nonscheduled transportation | Attending provider and NPI present |
| FL 77 operating provider | Required when a surgical procedure code is on the claim | Operating provider present on any claim with a surgical code |
The principal diagnosis rule has a billing consequence beyond the edit. Chapter 25 says entering any diagnosis other than the principal diagnosis may result in an incorrect DRG assignment and cause the hospital to be paid incorrectly under PPS. Where the diagnosis is a symptom with no definitive diagnosis, report the symptom, and if a definitive diagnosis is made during the outpatient evaluation, report that instead.
How do you work a returned UB-04 claim?
What does a rejected outpatient claim look like?
The values below are made up for illustration.
All three were fixed in one pass and the claim went out as new. None of the three needed a coder, which is why a pre-release locator check pays for itself.
How do we handle it?
Our hospital and facility billing team runs UB-04 accuracy checks on bill type, revenue codes, patient status, condition and occurrence codes, authorization requirements and payer-specific rules before a claim is released. To see how your own rejections break down by locator, book a call.
- Medicare Claims Processing Manual, Chapter 25: Completing and Processing the Form CMS-1450 Data Set · CMS
- Medicare Billing: CMS-1450 and 837I (MLN006926) · CMS
- Claim Adjustment Reason Codes · X12
- Remittance Advice Remark Codes · X12
We check every rule, code and deadline against the official source. See our editorial policy.
Common questions
Straight answers from the team that does the work.
Ask a billing lead directly. A 20-minute call, Monday to Friday, 9am to 5pm Eastern.
01Which UB-04 form locators cause the most claim rejections?
No official source ranks them. The locators where Chapter 25 sets a hard requirement or format include FL 4 type of bill, FL 6 statement period, FL 17 discharge status, FL 42 and FL 44 revenue and HCPCS pairing, FL 45 line dates, FL 56 billing NPI, FL 63 authorization and FL 67 diagnosis. Your clearinghouse report shows your own order.
02What is the difference between a rejection and a denial?
A rejection stops the claim before it is adjudicated because of a format or data problem, so it can be corrected and sent again as a new claim. A denial is a payer decision on a claim it accepted and processed, and it follows the appeal path in the payer's rules.
03Does FL 67 need a decimal point?
No. Chapter 25 says reporting the decimal between the third and fourth digit is unnecessary because it is implied. It also says to enter the full ICD-10-CM code, which is seven characters where applicable, and not to fill a shorter code with zeros.
04Is the UB-04 patient sex field limited to two values?
On the Medicare instructions, yes. Chapter 25 says the provider enters an M for male or an F for female for FL 11, recorded at admission, outpatient service or start of care. Check a commercial payer's manual for its own rules.
Talk to a billing lead.
A 20-minute call about your payers, volume and setup. Monday to Friday, 9am to 5pm Eastern.