UB04 Field 45: Service Date

Overview

Field 45, Service Date, is a required line-item date field on the UB‑04 claim form ^[1]. For outpatient services, CMS mandates that hospitals, Community Mental Health Centers (CMHCs), and most other providers report the specific date of service for each line item on the bill ^[2]. This requirement applies even when the “from” and “through” dates on the claim are identical ^[2]. The field is essential for proper payment adjudication, as it allows payers to match each revenue code, procedure code, or drug code to the exact date on which the service was rendered ^[2]. Both CMS and state Medicaid programs, such as Maryland Medicaid, require this field for outpatient claims ^[3]; ^[1]. Accurate completion of Field 45 is critical for audit compliance and to avoid claim rejections or payment delays ^[3].

When to Use

Field 45 must be completed on every UB‑04 claim that includes revenue codes, procedure codes, or drug codes for outpatient services ^[2]. This includes claims from hospitals (excluding Critical Access Hospitals, Indian Health Service hospitals, and hospitals in American Samoa, Guam, and Saipan) and CMHCs ^[2]. For outpatient claims, a separate line with its own service date is required for each distinct date of service, even if all dates fall within a single statement period ^[2]. The field is also used when the claim contains multiple revenue lines; each line’s service date must reflect the actual day the line‑item service was provided ^[2]. Failure to include the service date when required will result in a billing error and likely denial ^[3].

Step-by-Step Claim Example

Consider a patient who receives three distinct outpatient services: a lab test on June 1, 2025, a radiology exam on June 2, 2025, and a separate visit to a CMHC on June 3, 2025. The provider must submit a UB‑04 claim with a statement covers period (FL 6) of 06/01/2025 – 06/03/2025. On the claim detail, each line item is entered with its corresponding revenue code and procedure code. For the CMHC visit on June 3, a third line includes revenue code 090X with HCPCS code 90837, and Field 45 is “06032025” ^[2]. Each line also reports units (FL 46) and charges (FL 47). The payer uses the service date in FL 45 to validate medical necessity, date‑of‑service edits, and correct coding ^[2]. If the claim were for an inpatient stay, Field 45 would be left blank because the statement period already covers the entire admission ^[2]. This example demonstrates the critical distinction between outpatient line‑item dating and the inpatient “from/through” approach.

Common Mistakes & Audit Red Flags

A frequent error is omitting Field 45 on outpatient claims where revenue codes, procedure codes, or drug codes appear, leading to automatic denial by Medicare and many other payers ^[2]. Another mistake is entering a date that falls outside the statement covers period (FL 6); auditors will flag this as a logical inconsistency ^[2]. Some providers incorrectly use the same date for all lines when services were actually rendered on different days – this misrepresents the date of service and can trigger billing compliance reviews ^[2]. For CAHs, Indian Health Service hospitals, and hospitals in certain territories, the requirement to complete FL 45 on outpatient claims is explicitly waived; billing staff at these facilities must know they are exempt and should not add the field unnecessarily ^[2]. Also, when a claim includes a drug code (e.g., J-codes) and a service date is omitted, payers may assume the date is the “through” date of the statement period, which could cause payment errors ^[2]. Auditors cross‑reference FL 45 with the procedure code and revenue code to ensure the service was appropriate for that date; any mismatch can result in recoupment ^[3]. Providers should also verify that their billing software correctly maps the service date from clinical documentation to Field 45, as system errors are a common source of audit findings ^[1].

Related Codes/Fields

The following table lists UB‑04 fields and external codes frequently referenced together with Field 45.

Field or Code	Name / Description	Relationship to FL 45
FL 6	Statement Covers Period (From/Through)	Defines the overall date range; FL 45 dates must fall inside this range for outpatient claims [2].
FL 42	Revenue Code	Each revenue code line must have its own service date in FL 45 [2].
FL 44	HCPCS / RATES / HIPPS Rate Code	Procedure or drug codes on a line require a service date in FL 45 [2].
FL 46	Units of Service	Units are reported per date; FL 45 indicates the specific date of those units [1].
FL 47	Total Charges	Charges on each line are tied to the service date in FL 45 for pricing and audit [1].
FL 31–34	Occurrence Codes and Dates	These fields capture non‑routine dates (e.g., admission, discharge) separate from line‑item service dates in FL 45 [1].
ICD‑10‑CM/PCS	Diagnosis/Procedure Codes	While not on the same line, the diagnosis codes in FL 67 must be consistent with the service date in FL 45 for medical necessity [3].

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References

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