UB04 Field 49: Future Use

Overview

Field 49 (Box 49) of the UB-04 claim form is designated as “Reserved for Assignment by NUBC” and is not used in current billing operations. The National Uniform Billing Committee (NUBC) reserves this field for future assignment, meaning providers must leave it blank. The Maryland Medicaid UB-04 instructions list FL 49 as “Reserved for Assignment by NUBC” in the form’s table of contents, alongside other reserved fields such as FL 37 (NOT USED) and FL 68 (Reserved for Assignment by NUBC) ^[1]. Medicare explicitly states that FL 49 is “(Untitled) Not used,” and any data entered in this field will be ignored by claims processing systems ^[2]. This policy is reinforced by CMS transmittal R1915CP, which repeats the instruction: “FL 49 - (Untitled) Not used” ^[3]. Because the field is reserved, it carries no impact on claim adjudication, payment, or audit trails. Providers must ensure that no information is inadvertently placed in Box 49, as doing so could trigger unnecessary scrutiny or system errors. The UB-04 form’s structure places FL 49 between FL 48 (Non-Covered Charges) and FL 50 (Payer Name), and its emptiness is intentionally maintained for potential future standardization ^[1]. Understanding this status helps billers avoid confusion and comply with payer-specific requirements.

When to Use

Field 49 is never populated in any claim submission. According to Medicare’s claims processing manual, the field is explicitly “Not used” and any data entered will be ignored ^[2]. This directive applies to all UB-04 claims—inpatient, outpatient, and other institutional encounters—regardless of payer (Medicare, Medicaid, commercial). The Maryland Medicaid billing instructions reaffirm that FL 49 is “Reserved for Assignment by NUBC,” meaning it has no current defined purpose ^[1]. The only “use” of this field is to remain blank. Providers should treat FL 49 as a permanent placeholder that must not contain any characters, spaces, or symbols. In summary, the correct and only action for this field is to leave it empty.

Step-by-Step Claim Example

Consider a UB-04 claim for an outpatient hospital visit. The biller completes the form line by line. For Line 49 (Field 49), the biller must ensure the box is entirely blank. The following illustrates a typical claim segment around FL 49:

• FL 42 (Revenue Code): Enter the appropriate revenue code (e.g., 0510 for clinic visit). ^[1].
• FL 43 (NDC): If applicable, report the National Drug Code.
• FL 44 (HCPCS/RATES/HIPPS): Enter the procedure code.
• FL 45 (Service Date): Show the date of service.
• FL 46 (Units): Enter the number of units.
• FL 47 (Total Charges): Enter the total charge for the line.
• FL 48 (Non-Covered Charges): If any portion is non-covered, report the amount; otherwise leave blank.
• FL 49: Leave blank. Do not enter a dash, zero, or any text. ^[2].
• FL 50 (Payer Name): On line A, if Medicare is primary, enter “Medicare.” ^[2].

After completing all lines, the claim is submitted via the facility’s billing system. The system should automatically enforce an empty FL 49; if not, the biller manually clears the field. The claim is then edited by a clearinghouse; any data in FL 49 should trigger a warning or rejection based on payer standards. Once the claim is accepted, FL 49 has no role in pricing or adjudication. The final claim image will show an empty Box 49, consistent with NUBC reservation ^[3].

Common Mistakes & Audit Red Flags

Although FL 49 is rarely used, several mistakes still occur:

1. Entering placeholder text – Some billers add “N/A,” “0,” or a dash, mistakenly believing it is required. However, Medicare and Medicaid explicitly state the field is not used, and any data entered will be ignored ^[2]. While ignored, such characters can cause system-level warnings or delays if a clearinghouse applies strict formatting rules.

2. Confusing FL 49 with FL 48 or FL 50 – Because FL 48 is “Non-Covered Charges” and FL 50 is “Payer Name,” billers sometimes accidentally shift entries into FL 49 if they skip a column. For example, if a biller mistakenly places a payer name in FL 49, the claim may still process but the payer name will not be recognized, leading to potential denials. Cross-referencing the form’s table of contents helps avoid this ^[1].

3. Using FL 49 for internal tracking – Some providers attempt to use the field for internal reference numbers or notes. This is not allowed. NUBC has reserved the field exclusively for future assignment, and no authorized use exists today ^[3].

4. Audit red flags – While FL 49 data is typically ignored, a filled Field 49 can draw unnecessary attention from auditors who may question whether the provider is attempting to hide or miscode information. An empty FL 49 is the expected standard. If a claim contains unexpected data in reserved fields, auditors may flag the entire claim for review, delaying payment.

5. System auto-population – Medicare-certified software sometimes pre-fills FL 49 with a space or zero. Providers must review output and strip any content that is not explicitly required by the NUBC specifications. The safest practice is to export a blank file for this field ^[2].

Related Codes/Fields

The following table lists fields adjacent to FL 49 on the UB-04 form, as well as other reserved or unused fields. Descriptions are based solely on the provided sources.

Field Number	Field Name / Description	Source & Usage
FL 37	NOT USED	Reserved; no current function. [1]
FL 48	Non-Covered Charges	Reports charges not covered by the primary payer. Leave blank if none. [1]
FL 49	Reserved for Assignment by NUBC	Not used. Leave empty. [2] [3]
FL 50	Payer Name	Enter payer name on line A (e.g., “Medicare” for Medicare primary). [2]
FL 68	Reserved for Assignment by NUBC	Another reserved field, similar to FL 49. [1]

All field references above are drawn from the Maryland Medicaid UB-04 instructions and the CMS Chapter 25 manual. Note that the “PAGE ____ OF ____” and creation date information should appear on line 23 of each UB-04 page, not in FL 49 ^[2].

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References

[1] Maryland Medicaid — https://health.maryland.gov/mmcp/provider/Documents/ffs-billing/UB04-Hospital-Billing-Instructions%20%281%29.pdf

[2] CMS Chapter 25 — https://www.cms.gov/regulations-and-guidance/guidance/manuals/downloads/clm104c25.pdf

[3] CMS R1915CP — https://www.cms.gov/Regulations-and-Guidance/Guidance/Transmittals/downloads/R1915CP.pdf