UB04 Field 13: Admission Hour

Overview

Field 13 – Admission Hour captures the hour during which a patient was admitted for inpatient or outpatient care, using a 24-hour code structure (00–23). The requirements for this field vary by payer. According to ^[1], the admission hour is required on all inpatient claims (except bill type 21x) and optional for outpatient billing. The code table lists 00 (12:00–12:59 midnight) through 23 (11:00–11:59), with noon represented by code 12. ^[1] stipulates that the entry must be the hour when the patient was admitted for inpatient or outpatient care. In contrast, the ^[2] explicitly states that FL 13 – Admission Hour is not required and that if submitted, the data will be ignored. This discrepancy means providers must follow the rules of their specific payer (e.g., state Medicaid vs. Medicare) when completing the field. The field appears in Box 13 of the UB-04 form.

When to Use

Determining when to populate FL 13 depends on the payer’s instructions. For Maryland Medicaid, the field is mandatory on all inpatient claims except for type of bill 21x (intermediate care facilities); for outpatient billing it is optional. ^[1] requires the hourly code from the standard table (e.g., code 00 for midnight, code 12 for noon). For Medicare claims governed by CMS, the field is never required and any submitted value will be ignored. ^[2] states plainly: “FL 13 – Admission Hour Not Required. If submitted, the data will be ignored.” Therefore, providers billing Medicare should leave the field blank unless their intermediary or state-specific contract mandates otherwise. For other commercial payers, verify their billing instructions, as some may adopt the UB-04 standard of required inpatient submission.

Step-by-Step Claim Example

The following example follows Maryland Medicaid rules (inpatient required, optional for outpatient). Use the 24-hour code table provided.

• Step 1: Determine the actual admission time. Patient admitted at 2:35 PM (14:35).
• Step 2: Identify the corresponding hour code. 14:35 falls within the hour 14:00–14:59, so code 14.
• Step 3: Enter the two-digit code in Box 13. Write 14.
• Step 4: Ensure the admission date in FL 12 is consistent. The admission date must be between the “From” and “Through” dates (FL 6) and can be no more than 3 calendar days after the “From” date (except for Type of Bill Frequency 3 or 4). ^[1]
• Step 5: For a midnight admission (12:00–12:59 AM), use code 00; for noon (12:00–12:59 PM), use code 12. Do not use 24 – the table stops at 23.

If billing Medicare, simply leave Box 13 blank; any entry will be ignored. ^[2]

Common Mistakes & Audit Red Flags

• Providing admission hour for Medicare claims – This is wasteful because the data will be ignored, but it does not harm the claim. However, if a provider’s system unexpectedly populates the field, no audit flag is raised. ^[2]
• Missing required field for Maryland inpatient – If the admission hour is omitted on a non‑21x inpatient claim, the claim may be rejected. ^[1] requires the field for all inpatient claims except bill type 21x.
• Using wrong code format – Codes must be exactly two digits (e.g., 01, 12, 23). Entering 1 instead of 01 or using non‑numeric values may cause edits.
• Confusing midnight and noon – Code 00 is midnight (12:00–12:59 AM), code 12 is noon (12:00–12:59 PM). Reversing them could lead to an invalid admission hour.
• Submitting admission hour for bill type 21x – Maryland exempts intermediate care facilities; including the field is optional but not required. ^[1]
• Inconsistent admission date – The admission hour should correspond to the admission date in FL 12. Although no source explicitly links the two, an unlikely hour (e.g., admitting at 3 AM but FL 12 shows a future date) could attract manual review.

Related Codes/Fields

Field Number	Field Name	Relationship to FL 13
FL 12	Admission/Start of Care Date	Provides the date context for the admission hour; the date must align with the hour. [1]
FL 14	Priority (Type) of Visit	Indicates the admission priority (e.g., 1=Emergency). Required for inpatient only; complements the admission hour. [2]
FL 6	Statement Covers Period (From/Through)	Admission date (FL 12) must fall within or no more than 3 days after “From” date. [1]
FL 10	Patient Birth Date	Not directly related, but used for patient identification. [1]
FL 11	Patient Sex	Optional; recorded at admission. [1]
Type of Bill	(on UB-04 header)	Determines whether FL 13 is required (e.g., bill type 21x exempt). [1]

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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 R1915CP transmittal — https://www.cms.gov/Regulations-and-Guidance/Guidance/Transmittals/downloads/R1915CP.pdf