UB04 Admission Hour Code 02: 02:00 AM - 02:59 AM

Overview

The UB‑04 admission hour code 02 corresponds to the time interval 02:00 AM – 02:59 AM in military (24‑hour) format. This code is reported in Field 13 (Admission/Start of Care Date) of the UB‑04 claim form and is required only on inpatient bills. The hour code represents the specific hour of admission, with values ranging from 00 (12:00 AM) through 23 (11:00 PM). ^[1] explicitly defines that code 01 equals 1:00 AM, code 02 equals 2:00 AM, and so forth up to code 23 for 11:00 PM. Code 02 therefore indicates that the patient was admitted between 2:00 AM and 2:59 AM on the date recorded in Field 13. MassHealth’s UB‑04 billing guide states that providers must submit claims electronically unless an exemption is approved, but the paper form instructions remain the authoritative reference for manual processing. ^[2] In all cases, the admission hour code is a critical data element for verifying the timing of inpatient care and for processing Medicare and Medicaid claims correctly.

When to Use

Use admission hour code 02 when a patient’s inpatient admission occurs at any time between 2:00 AM and 2:59 AM (military time 02:00 through 02:59) on the date of admission. According to CMS, the admission hour code must represent the “hour of admission in military time,” and code 02 is the exact identifier for that one‑hour span. ^[1] This code is mandatory on inpatient bills only; outpatient bills should use Field 13 for the start‑of‑care date but may not require the hour code on all claims. For example, if a patient arrives at the hospital at 2:15 AM, the provider should enter the admission date in Field 13 followed by code 02. The coding convention applies uniformly across all payers (Medicare, Medicaid, commercial insurers) that follow the UB‑04 standard. MassHealth’s billing guide does not alter the CMS definition of admission hour codes, so code 02 applies equally to MassHealth‑covered admissions. ^[2] Never use code 02 for an admission that starts at 1:59 AM (use 01) or at 3:00 AM (use 03). The correct application of this code supports accurate length‑of‑stay calculations, proper provider payment, and compliance with regulatory reporting requirements.

Step‑by‑Step Claim Example

Consider a 68‑year‑old Medicare beneficiary admitted through the emergency department at 2:42 AM on January 15, 2025, for acute chest pain. The inpatient admission is recorded on the UB‑04 claim as follows:

1. Field 12 (Admission Date): Enter 01/15/2025 (or appropriate date format per payer).
2. Field 13 (Admission/Start of Care Date): Enter 01/15/2025. Immediately to the right of the date, insert the hour code 02. This tells the payer that admission occurred during the 2:00‑2:59 AM hour. ^[1]
3. Field 14 (Priority of Admission): Code 1 for emergency admission.
4. Field 15 (Source of Admission): Code 1 for emergency room referral.
5. Field 16 (Discharge Hour): If applicable, enter the discharge hour code.

The completed Fields 12‑13 appear as:
01/15/2025 02 (assuming space‑delimited). The claim is then submitted electronically per MassHealth’s all‑electronic policy, although the paper form instructions govern the coding. ^[2] Using code 02 ensures the admitting hospital’s clock‑time is precisely documented, supporting accurate DRG assignment and outlier payment calculations.

Common Mistakes & Audit Red Flags

Incorrect hour code: Using code 01 for an admission that occurred at 2:15 AM is a frequent error. CMS clearly defines code 02 as the only valid code for 2:00‑2:59 AM, and any deviation triggers an edit. ^[1]
Missing leading zero: Entering “2” instead of “02” can be misinterpreted as a two‑character date component or may be rejected by electronic front‑end edits. The code must always be two digits.
Outpatient misuse: Applying code 02 on an outpatient claim when no inpatient admission occurred is incorrect. Field 13 is required on inpatient bills only; for outpatient, the hour code should be left blank or omitted per payer instructions.
Inconsistent with time of admission: If the medical record shows “2:00 AM” but the code entered is 01, the claim may be flagged for mismatch during medical review.
Paper vs. electronic discrepancies: MassHealth requires electronic submission, so the hour code must match the electronic format exactly. ^[2]
Rounding errors: Do not round 1:59 AM to 02; use code 01. Similarly, 3:00 AM is code 03, not 02.
Audit red flags: Claims with code 02 but no corresponding admission date in Field 13, or with hour codes that contradict the source of admission (e.g., elective admission at 2:00 AM may require justification). Correct code usage reduces claim denials and helps avoid payer post‑payment audits.

Related Codes/Fields

The table below lists fields and codes that interact with admission hour code 02 on the UB‑04 claim form. All references are based on the CMS transmittal and the MassHealth UB‑04 guide.

Field Number	Name / Code Set	Relation to Hour Code 02	Source
12	Admission Date	Provides the calendar date; the hour code 02 is appended to the date in Field 13 (not Field 12).	[1]
13	Admission/Start of Care Date	Primary field for the date and hour code. Code 02 must be placed immediately after the date.	[1]
14	Priority of Admission	Indicates type of admission (e.g., emergency, urgent, elective). No direct relation, but hour codes like 02 often pair with emergency (code 1).	[1]
15	Source of Admission	Documents where patient came from (e.g., ER, clinic). Hour code may be consistent with ER arrival times.	[1]
16	Discharge Hour	Discharge hour code (00‑23) used on inpatient bills. Should be later than admission hour (e.g., code 02 admission cannot have discharge hour 01).	[1]
01‑23 (hour codes)	Admission Hour Codes	All 24 possible hour codes. Code 02 is the third code (00, 01, 02…). Adjacent codes 01 (1:00‑1:59 AM) and 03 (3:00‑3:59 AM) are common confusion risks.	[1]
–	Military Time Convention	The entire hour code system uses 24‑hour clock. Code 02 corresponds to 02:00‑02:59 AM. No other conventions are valid on UB‑04.	[1]

Note: The MassHealth UB‑04 guide provides general billing instructions but does not list individual hour codes; the authoritative source for code‑to‑time mapping is the CMS transmittal. ^[2] Under field 13 of the CMS instruction, the hour code must be two digits and cannot exceed 23.

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References

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

[2] MassHealth UB-04 Guide — https://www.mass.gov/doc/ub-04-billing-guide-0/download