UB04 Field 13: Admission Hour

Overview

Field 13: Admission Hour is a mandatory data element on the UB-04 (CMS-1450) claim form used to report the specific hour a patient was admitted for inpatient care or began a period of observation. This field is located in the upper right quadrant of the form, immediately following the admission date. It captures the time of admission using a two-digit numeric code representing a 24-hour clock cycle.

The National Uniform Billing Committee (NUBC) requires this field for all inpatient institutional claims to establish the start of the "medical necessity" window and to calculate the length of stay accurately. For outpatient claims, requirements vary by payer, but it is frequently required for Ambulatory Surgical Centers (ASC) and emergency department visits that result in a transfer. The hour reported must reflect the time the formal admission order was written or the time the patient arrived at the specific unit for care CMS Pub. 100-04 Chapter 25.

When to Use This Field

Field 13 is required for all Inpatient (TOB 11X) and Swing Bed (TOB 18X) claims. It is also critical for Observation Services to determine if the 24-hour or 48-hour thresholds for specific reimbursement tiers are met.

Scenario 1: Inpatient Acute Care Admission A patient arrives at the Emergency Department at 10:45 PM. After stabilization and testing, the physician signs the inpatient admission order at 1:15 AM the following day. The biller must report the admission date as the day the order was signed and use code 01 in Field 13 to represent the 01:00 AM – 01:59 AM window. Reporting the ED arrival time instead of the admission order time is a common compliance error.

Scenario 2: Newborn Deliveries For newborn claims (TOB 11X), the admission hour must match the actual time of birth. If a baby is delivered at 2:30 PM, the biller enters code 14 (02:00 PM – 02:59 PM). This time must align with the birth weight and clinical indicators reported in the medical record to avoid DRG (Diagnosis Related Group) mismatches NUBC UB-04 Manual.

Step-by-Step Claim Example

Patient Scenario: A 68-year-old Medicare beneficiary presents for a scheduled total hip arthroplasty. The patient checks into the surgical suite at 06:30 AM. The surgery is completed, and the patient is moved to a post-surgical inpatient bed. The formal inpatient admission order is timed and signed by the surgeon at 09:15 AM on October 12, 2023.

Field Values:

Field 12 (Admission Date): 101223
Field 13 (Admission Hour): 09
Field 14 (Priority (Type) of Admission): 3 (Elective)
Field 17 (Stat): 01 (Discharged to Home)

Payer Response: The Medicare Administrative Contractor (MAC) validates Field 13 against the Revenue Code 0120 (Room & Board) start time. Because the admission hour (09) precedes the first midnight of the stay, the system calculates the first billable day correctly. If the biller had incorrectly entered "06" (the arrival time), but the physician's order was not signed until "09," an auditor might flag the claim for "upcoding" the length of stay if that three-hour difference pushed the patient into a higher-tier reimbursement window Medicare Claims Processing Manual Chapter 25.

Common Mistakes & Audit Red Flags

Using 12-Hour Format: One of the most frequent denials occurs when billers use "01" for 1:00 PM. All times must follow the 24-hour cycle. 1:00 PM must be reported as 13.
Code 99 Overuse: Code 99 (Unknown) is valid but triggers manual reviews by many commercial payers. If the medical record contains a nursing intake note or a physician order, using "99" is considered a failure to provide a complete claim and may result in a Return to Provider (RTP) status.
Inconsistency with Field 16: Field 16 (Discharge Hour) and Field 13 are used together to calculate total hours for observation. If Field 13 is later than Field 16 on a single-day stay, the claim will automatically reject due to "negative duration" logic in the payer's adjudication system Occurrence Codes - JE Part A - Noridian.

Admission Hour Codes

References

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FormJuicer Data Insights

This guide was developed by the FormJuicer Billing Research Team using official CMS and NUBC guidelines, combined with patterns observed from processing thousands of real UB-04 documents through our system.

Last Updated: 2026-05-01

Sources: CMS Pub. 100-04 Chapter 25, NUBC Official UB-04 Manual, Medicare Contractor Bulletins (Noridian, Palmetto, CGS)