UB04 Admission Hour Code 05: 05:00 AM - 05:59 AM

Overview

The UB-04 form uses Field Locator (FL) 13 – Admission Hour to record the precise hour when a patient was admitted for either inpatient or outpatient care. Code 05 specifically denotes the time interval 05:00 AM to 05:59 AM ^[1]. According to the Maryland Medicaid billing instructions, this field is required on all inpatient claims except for bill type 21x (intermediate care facilities); it is optional for outpatient billing ^[1]. The source provides a comprehensive code – time mapping, where each hour of the day is represented by a two-digit code (00 through 23). For morning hours, codes 00 through 11 cover midnight to 11:59 AM, with 05 falling between 04 and 06. This structure ensures a standardised reporting that avoids ambiguity in admission timing, which is critical for utilization review, length-of-stay calculations, and payer audits ^[1]. Providers must note that the first month of billing may have different requirements; the source specifically references “e first month of billing only” as a possible modifier, though the core rule remains that FL 13 is mandatory for most inpatient admissions ^[1].

When to Use

Code 05 should be used only when the patient’s admission occurred between 05:00 AM and 05:59 AM, regardless of the day of the week or the type of admission (emergency, urgent, elective, etc.) ^[1]. The source states that the admission hour code is “Required on all inpatient claims except for bill type 21x (intermediate care facilities).” Therefore, for any inpatient admission falling within this time window, code 05 is mandatory [Maryland Medicaid — FL 13 (Code 05)](https://health.maryland.gov/mmcp/provider/Documents/ffs-billing/UB04-Hospital-Billing-Instructions%20%281%29.pdf]. For outpatient services, the field is optional, meaning a provider may choose to leave FL 13 blank for outpatient claims; however, if it is completed, the correct hour‑based code must be used [Maryland Medicaid — FL 13 (Code 05)](https://health.maryland.gov/mmcp/provider/Documents/ffs-billing/UB04-Hospital-Billing-Instructions%20%281%29.pdf]. The documentation provided by Maryland Medicaid explicitly lists code 05 as “05:00-05:59.” No other code should be substituted for this interval. Also note that bill type 21x (intermediate care facilities) is explicitly exempt from the admission hour requirement; for those claims, code 05 is not needed even if the patient was admitted during that hour [Maryland Medicaid — FL 13 (Code 05)](https://health.maryland.gov/mmcp/provider/Documents/ffs-billing/UB04-Hospital-Billing-Instructions%20%281%29.pdf]. Practically, code 05 is commonly used for patients admitted in early morning hours, such as those arriving at the emergency department after midnight and being formally admitted after 5 AM, or for scheduled surgical admissions occurring at that time.

Step-by-Step Claim Example

Scenario: A patient is admitted to an acute care hospital (bill type 111) on February 5, 2025 at 05:30 AM. The claim is for the first month of billing.
Step 1 – Determine required field: Because this is an inpatient claim and not bill type 21x, FL 13 is mandatory ^[1].
Step 2 – Identify the hour: The time of admission falls between 05:00 and 05:59 AM. According to the source table, code 05 corresponds to that interval ^[1].
Step 3 – Enter on the UB-04: On FL 13 of the claim form, enter the two‑digit code 05. Do not add colons or AM/PM.
Step 4 – Verify other fields: Ensure no other codes (e.g., 04 for 04:00–04:59 or 06 for 06:00–06:59) are mistakenly used.
Step 5 – Submit: The claim, with code 05 in FL 13, is now accurate for the admission hour. The source does not provide additional claim‑level data, so this example assumes all other required fields (e.g., FL 14 Priority of Visit) are completed per institutional guidelines.

Common Mistakes & Audit Red Flags

1. Using the wrong code for the time interval: A frequent error is confusing code 05 with code 17 (which also covers 05:00–05:59 but in the PM block). The source table clearly distinguishes AM codes (00–11) from PM codes (12–23). Code 05 is for morning, code 17 is for evening ^[1]. Auditors will flag a mismatch if the patient’s medical record shows 5 PM admission but code 05 appears.
2. Omitting the field on inpatient claims: The source mandates that FL 13 is required for all inpatient admissions except bill type 21x ^[1]. Leaving it blank on an inpatient UB-04 can cause a claim rejection or delay.
3. Using code 05 for outpatient claims when not optional: While FL 13 is optional for outpatient billing, if the provider decides to populate it, they must use the correct code for the actual admission hour. Using an arbitrary code like 05 when the outpatient visit occurred at a different time is a misrepresentation ^[1].
4. Ignoring the first‑month billing note: The source text begins with “e first month of billing only.” This may indicate that for initial billing periods, special rules apply. Providers should verify whether the admission hour field is handled differently in the first month; failing to do so could trigger an audit ^[1].
5. Mixing up code 00 (midnight) and code 05: Admissions at exactly 5 AM must use code 05, not 00. The smallest time granularity is the hour; the code represents the entire hour range.

Related Codes/Fields

The source provides a complete table for codes 00–23 on FL 13. Below is a summary of all admission hour codes from the Maryland Medicaid document. Note that code 05 is specifically for 05:00–05:59 AM, while code 17 is for the same hour in the PM period ^[1]. Additional related fields include FL 14 (Priority of Visit), which is required for inpatient billing but is separate from the admission hour.

Code	Time (AM/PM)	Equivalent PM Code (if applicable)
00	12:00–12:59 Midnight	12 (12:00–12:59 Noon)
01	01:00–01:59 AM	13 (01:00–01:59 PM)
02	02:00–02:59 AM	14 (02:00–02:59 PM)
03	03:00–03:59 AM	15 (03:00–03:59 PM)
04	04:00–04:59 AM	16 (04:00–04:59 PM)
05	05:00–05:59 AM	17 (05:00–05:59 PM)
06	06:00–06:59 AM	18 (06:00–06:59 PM)
07	07:00–07:59 AM	19 (07:00–07:59 PM)
08	08:00–08:59 AM	20 (08:00–08:59 PM)
09	09:00–09:59 AM	21 (09:00–09:59 PM)
10	10:00–10:59 AM	22 (10:00–10:59 PM)
11	11:00–11:59 AM	23 (11:00–11:59 PM)

• FL 14 Priority (Type) of Visit – Required for inpatient billing only; it captures the urgency (emergency, urgent, elective) of the admission. The source mentions this field directly after the admission hour table ^[1].
• Bill type 21x – Intermediate care facilities are explicitly excluded from the admission hour requirement; no code is needed in FL 13 for those claims [Maryland Medicaid — FL 13 (Code 05)](https://health.maryland.gov/mmcp/provider/Documents/ffs-billing/UB04-Hospital-Billing-Instructions%20%281%29.pdf].

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References

[1] Maryland Medicaid — FL 13 (Code 05) — https://health.maryland.gov/mmcp/provider/Documents/ffs-billing/UB04-Hospital-Billing-Instructions%20%281%29.pdf